diff --git a/client.go b/client.go
index 15bf202..db0eccf 100644
--- a/client.go
+++ b/client.go
@@ -4,26 +4,46 @@
 package gomatrix
 
 import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 	"path"
+	"strconv"
 	"sync"
+	"time"
 )
 
 // Client represents a Matrix client.
 type Client struct {
-	HomeserverURL   *url.URL        // The base homeserver URL
-	Prefix          string          // The API prefix eg '/_matrix/client/r0'
-	UserID          string          // The user ID of the client. Used for forming HTTP paths which use the client's user ID.
-	AccessToken     string          // The access_token for the client.
-	syncingMutex    sync.Mutex      // protects syncingID
-	syncingID       uint32          // Identifies the current Sync. Only one Sync can be active at any given time.
-	Client          *http.Client    // The underlying HTTP client which will be used to make HTTP requests.
-	FilterStorer    FilterStorer    // Interface for saving and loading the filter ID for sync.
-	NextBatchStorer NextBatchStorer // Interface for saving and loading the "next_batch" sync token.
+	HomeserverURL *url.URL     // The base homeserver URL
+	Prefix        string       // The API prefix eg '/_matrix/client/r0'
+	UserID        string       // The user ID of the client. Used for forming HTTP paths which use the client's user ID.
+	AccessToken   string       // The access_token for the client.
+	syncingMutex  sync.Mutex   // protects syncingID
+	syncingID     uint32       // Identifies the current Sync. Only one Sync can be active at any given time.
+	Client        *http.Client // The underlying HTTP client which will be used to make HTTP requests.
+	Syncer        Syncer       // The thing which can process /sync responses
 	// TODO: Worker and Rooms
 }
 
+// HTTPError An HTTP Error response, which may wrap an underlying native Go Error.
+type HTTPError struct {
+	WrappedError error
+	Message      string
+	Code         int
+}
+
+func (e HTTPError) Error() string {
+	var wrappedErrMsg string
+	if e.WrappedError != nil {
+		wrappedErrMsg = e.WrappedError.Error()
+	}
+	return fmt.Sprintf("%s: %d: %s", e.Message, e.Code, wrappedErrMsg)
+}
+
 // BuildURL builds a URL with the Client's homserver/prefix/access_token set already.
 func (cli *Client) BuildURL(urlPath ...string) string {
 	ps := []string{cli.Prefix}
@@ -58,6 +78,154 @@ func (cli *Client) BuildURLWithQuery(urlPath []string, urlQuery map[string]strin
 	return u.String()
 }
 
+// Sync starts syncing with the provided Homeserver. This function will block until a fatal /sync error occurs, so should
+// almost always be started as a new goroutine. If Sync() is called twice then the first sync will be stopped.
+func (cli *Client) Sync() error {
+	// Mark the client as syncing.
+	// We will keep syncing until the syncing state changes. Either because
+	// Sync is called or StopSync is called.
+	syncingID := cli.incrementSyncingID()
+	nextBatch := cli.Syncer.NextBatchStorer().LoadNextBatch(cli.UserID)
+	filterID := cli.Syncer.FilterStorer().LoadFilter(cli.UserID)
+	if filterID == "" {
+		filterJSON := cli.Syncer.FilterStorer().GetFilterJSON(cli.UserID)
+		resFilter, err := cli.CreateFilter(filterJSON)
+		if err != nil {
+			return err
+		}
+		filterID = resFilter.FilterID
+		cli.Syncer.FilterStorer().SaveFilter(cli.UserID, filterID)
+	}
+
+	for {
+		resSync, err := cli.SyncRequest(30000, nextBatch, filterID, false, "")
+		if err != nil {
+			duration, err2 := cli.Syncer.OnFailedSync(resSync, err)
+			if err2 != nil {
+				return err2
+			}
+			time.Sleep(duration)
+			continue
+		}
+
+		// Check that the syncing state hasn't changed
+		// Either because we've stopped syncing or another sync has been started.
+		// We discard the response from our sync.
+		if cli.getSyncingID() != syncingID {
+			return nil
+		}
+
+		// Save the token now *before* processing it. This means it's possible
+		// to not process some events, but it means that we won't get constantly stuck processing
+		// a malformed/buggy event which keeps making us panic.
+		cli.Syncer.NextBatchStorer().SaveNextBatch(cli.UserID, resSync.NextBatch)
+		if err = cli.Syncer.ProcessResponse(resSync, nextBatch); err != nil {
+			return err
+		}
+
+		nextBatch = resSync.NextBatch
+	}
+}
+
+func (cli *Client) incrementSyncingID() uint32 {
+	cli.syncingMutex.Lock()
+	defer cli.syncingMutex.Unlock()
+	cli.syncingID++
+	return cli.syncingID
+}
+
+func (cli *Client) getSyncingID() uint32 {
+	cli.syncingMutex.Lock()
+	defer cli.syncingMutex.Unlock()
+	return cli.syncingID
+}
+
+// StopSync stops the ongoing sync started by Sync.
+func (cli *Client) StopSync() {
+	// Advance the syncing state so that any running Syncs will terminate.
+	cli.incrementSyncingID()
+}
+
+// SendJSON sends JSON to the given URL. Returns an error if the response is not 2xx.
+func (cli *Client) SendJSON(method string, httpURL string, contentJSON interface{}) ([]byte, error) {
+	jsonStr, err := json.Marshal(contentJSON)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequest(method, httpURL, bytes.NewBuffer(jsonStr))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	res, err := cli.Client.Do(req)
+	if res != nil {
+		defer res.Body.Close()
+	}
+	if err != nil {
+		return nil, err
+	}
+	contents, err := ioutil.ReadAll(res.Body)
+	if res.StatusCode >= 300 || res.StatusCode < 200 {
+		return nil, HTTPError{
+			Code:    res.StatusCode,
+			Message: "Failed to " + method + " JSON: HTTP " + strconv.Itoa(res.StatusCode),
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+	return contents, nil
+}
+
+// CreateFilter makes an HTTP request according to http://matrix.org/docs/spec/client_server/r0.2.0.html#post-matrix-client-r0-user-userid-filter
+func (cli *Client) CreateFilter(filter json.RawMessage) (*RespCreateFilter, error) {
+	urlPath := cli.BuildURL("user", cli.UserID, "filter")
+	resBytes, err := cli.SendJSON("POST", urlPath, &filter)
+	if err != nil {
+		return nil, err
+	}
+	var filterResponse RespCreateFilter
+	if err = json.Unmarshal(resBytes, &filterResponse); err != nil {
+		return nil, err
+	}
+	return &filterResponse, nil
+}
+
+// SyncRequest makes an HTTP request according to http://matrix.org/docs/spec/client_server/r0.2.0.html#get-matrix-client-r0-sync
+func (cli *Client) SyncRequest(timeout int, since, filterID string, fullState bool, setPresence string) (*RespSync, error) {
+	query := map[string]string{
+		"timeout": strconv.Itoa(timeout),
+	}
+	if since != "" {
+		query["since"] = since
+	}
+	if filterID != "" {
+		query["filter"] = filterID
+	}
+	if setPresence != "" {
+		query["set_presence"] = setPresence
+	}
+	if fullState {
+		query["full_state"] = "true"
+	}
+	urlPath := cli.BuildURLWithQuery([]string{"sync"}, query)
+	req, err := http.NewRequest("GET", urlPath, nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := cli.Client.Do(req)
+	if res != nil {
+		defer res.Body.Close()
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	var syncResponse RespSync
+	err = json.NewDecoder(res.Body).Decode(&syncResponse)
+	return &syncResponse, err
+}
+
 // NewClient creates a new Matrix Client ready for syncing
 func NewClient(homeserverURL, userID, accessToken string) (*Client, error) {
 	hsURL, err := url.Parse(homeserverURL)
@@ -69,15 +237,21 @@ func NewClient(homeserverURL, userID, accessToken string) (*Client, error) {
 		HomeserverURL: hsURL,
 		UserID:        userID,
 		Prefix:        "/_matrix/client/r0",
+		Syncer: NewDefaultSyncer(
+			userID,
+			// By default, use an in-memory next_batch storer which will never save tokens to disk.
+			// The client will work with this storer: it just won't
+			// remember the token across restarts. In practice, a database backend should be used.
+			&InMemoryNextBatchStore{make(map[string]string)},
+			// By default, use an in-memory filter storer which will never save the filter ID to disk.
+			// The client will work with this storer: it just won't remember the filter
+			// ID across restarts and hence request a new one. In practice, a database backend should be used.
+			&InMemoryFilterStore{
+				Filter:       json.RawMessage(`{"room":{"timeline":{"limit":50}}}`),
+				UserToFilter: make(map[string]string),
+			},
+		),
 	}
-	// By default, use a no-op next_batch storer which will never save tokens and always
-	// "load" the empty string as a token. The client will work with this storer: it just won't
-	// remember the token across restarts. In practice, a database backend should be used.
-	cli.NextBatchStorer = NopNextBatchStore{}
-	// By default, use a no-op filter storer which will never save the filter ID and always
-	// "load" nothing. The client will work with this storer: it just won't remember the filter
-	// ID across restarts and hence request a new one. In practice, a database backend should be used.
-	cli.FilterStorer = NopFilterStore{}
 	// By default, use the default HTTP client.
 	cli.Client = http.DefaultClient
 
diff --git a/room.go b/room.go
index dde6aba..0533b3e 100644
--- a/room.go
+++ b/room.go
@@ -39,3 +39,12 @@ func (room Room) GetMembershipState(userID string) string {
 	}
 	return state
 }
+
+// NewRoom creates a new Room with the given ID
+func NewRoom(roomID string) *Room {
+	// Init the State map and return a pointer to the Room
+	return &Room{
+		ID:    roomID,
+		State: make(map[string]map[string]*Event),
+	}
+}
diff --git a/sync.go b/sync.go
index 03c2a2e..ca21be0 100644
--- a/sync.go
+++ b/sync.go
@@ -1,35 +1,218 @@
 package gomatrix
 
+import (
+	"encoding/json"
+	"fmt"
+	"runtime/debug"
+	"time"
+)
+
+// Syncer represents an interface that must be satisfied in order to do /sync requests on a client.
+type Syncer interface {
+	// Process the /sync response. The since parameter is the since= value that was used to produce the response.
+	// This is useful for detecting the very first sync (since=""). If an error is return, Syncing will be stopped
+	// permanently.
+	ProcessResponse(resp *RespSync, since string) error
+	// Interface for saving and loading the "next_batch" sync token.
+	NextBatchStorer() NextBatchStorer
+	// Interface for saving and loading the filter ID for sync.
+	FilterStorer() FilterStorer
+	// OnFailedSync returns either the time to wait before retrying or an error to stop syncing permanently.
+	OnFailedSync(res *RespSync, err error) (time.Duration, error)
+}
+
+// DefaultSyncer is the default syncing implementation. You can either write your own syncer, or selectively
+// replace parts of this default syncer (e.g. the NextBatch/Filter storers, or the ProcessResponse method).
+type DefaultSyncer struct {
+	UserID         string
+	Rooms          map[string]*Room
+	NextBatchStore NextBatchStorer
+	FilterStore    FilterStorer
+	listeners      map[string][]OnEventListener // event type to listeners array
+}
+
+// OnEventListener can be used with DefaultSyncer.OnEventType to be informed of incoming events.
+type OnEventListener func(*Event)
+
+// NewDefaultSyncer returns an instantiated DefaultSyncer
+func NewDefaultSyncer(userID string, nextBatch NextBatchStorer, filterStore FilterStorer) *DefaultSyncer {
+	return &DefaultSyncer{
+		UserID:         userID,
+		Rooms:          make(map[string]*Room),
+		NextBatchStore: nextBatch,
+		FilterStore:    filterStore,
+		listeners:      make(map[string][]OnEventListener),
+	}
+}
+
+// ProcessResponse processes the /sync response in a way suitable for bots. "Suitable for bots" means a stream of
+// unrepeating events.
+func (s *DefaultSyncer) ProcessResponse(res *RespSync, since string) (err error) {
+	if !s.shouldProcessResponse(res, since) {
+		return
+	}
+
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("ProcessResponse panicked! userID=%s since=%s panic=%s\n%s", s.UserID, since, r, debug.Stack())
+		}
+	}()
+
+	for roomID, roomData := range res.Rooms.Join {
+		room := s.getOrCreateRoom(roomID)
+		for _, event := range roomData.State.Events {
+			event.RoomID = roomID
+			room.UpdateState(&event)
+			s.notifyListeners(&event)
+		}
+		for _, event := range roomData.Timeline.Events {
+			event.RoomID = roomID
+			s.notifyListeners(&event)
+		}
+	}
+	for roomID, roomData := range res.Rooms.Invite {
+		room := s.getOrCreateRoom(roomID)
+		for _, event := range roomData.State.Events {
+			event.RoomID = roomID
+			room.UpdateState(&event)
+			s.notifyListeners(&event)
+		}
+	}
+	return
+}
+
+// OnEventType allows callers to be notified when there are new events for the given event type.
+// There are no duplicate checks.
+func (s *DefaultSyncer) OnEventType(eventType string, callback OnEventListener) {
+	_, exists := s.listeners[eventType]
+	if !exists {
+		s.listeners[eventType] = []OnEventListener{}
+	}
+	s.listeners[eventType] = append(s.listeners[eventType], callback)
+}
+
+// shouldProcessResponse returns true if the response should be processed. May modify the response to remove
+// stuff that shouldn't be processed.
+func (s *DefaultSyncer) shouldProcessResponse(resp *RespSync, since string) bool {
+	if since == "" {
+		return false
+	}
+	// This is a horrible hack because /sync will return the most recent messages for a room
+	// as soon as you /join it. We do NOT want to process those events in that particular room
+	// because they may have already been processed (if you toggle the bot in/out of the room).
+	//
+	// Work around this by inspecting each room's timeline and seeing if an m.room.member event for us
+	// exists and is "join" and then discard processing that room entirely if so.
+	// TODO: We probably want to process messages from after the last join event in the timeline.
+	for roomID, roomData := range resp.Rooms.Join {
+		for i := len(roomData.Timeline.Events) - 1; i >= 0; i-- {
+			e := roomData.Timeline.Events[i]
+			if e.Type == "m.room.member" && e.StateKey == s.UserID {
+				m := e.Content["membership"]
+				mship, ok := m.(string)
+				if !ok {
+					continue
+				}
+				if mship == "join" {
+					_, ok := resp.Rooms.Join[roomID]
+					if !ok {
+						continue
+					}
+					delete(resp.Rooms.Join, roomID)   // don't re-process messages
+					delete(resp.Rooms.Invite, roomID) // don't re-process invites
+					break
+				}
+			}
+		}
+	}
+	return true
+}
+
+// getOrCreateRoom must only be called by the Sync() goroutine which calls ProcessResponse()
+func (s *DefaultSyncer) getOrCreateRoom(roomID string) *Room {
+	room := s.Rooms[roomID]
+	if room == nil { // create a new Room
+		room = NewRoom(roomID)
+		s.Rooms[roomID] = room
+	}
+	return room
+}
+
+func (s *DefaultSyncer) notifyListeners(event *Event) {
+	listeners, exists := s.listeners[event.Type]
+	if !exists {
+		return
+	}
+	for _, fn := range listeners {
+		fn(event)
+	}
+}
+
+// NextBatchStorer returns the provided NextBatchStorer
+func (s *DefaultSyncer) NextBatchStorer() NextBatchStorer {
+	return s.NextBatchStore
+}
+
+// FilterStorer returns the provided FilterStorer
+func (s *DefaultSyncer) FilterStorer() FilterStorer {
+	return s.FilterStore
+}
+
+// OnFailedSync always returns a 10 second wait period between failed /syncs.
+func (s *DefaultSyncer) OnFailedSync(res *RespSync, err error) (time.Duration, error) {
+	return 10 * time.Second, nil
+}
+
 // NextBatchStorer controls loading/saving of next_batch tokens for users
 type NextBatchStorer interface {
-	// Save a next_batch token for a given user. Best effort.
-	Save(userID, nextBatch string)
-	// Load a next_batch token for a given user. Return an empty string if no token exists.
-	Load(userID string) string
+	// SaveNextBatch saves a next_batch token for a given user. Best effort.
+	SaveNextBatch(userID, nextBatch string)
+	// LoadNextBatch loads a next_batch token for a given user. Return an empty string if no token exists.
+	LoadNextBatch(userID string) string
 }
 
-// NopNextBatchStore does not load or save next_batch tokens.
-type NopNextBatchStore struct{}
+// InMemoryNextBatchStore stores next batch tokens in memory.
+type InMemoryNextBatchStore struct {
+	UserToNextBatch map[string]string
+}
 
-// Save does nothing
-func (s NopNextBatchStore) Save(userID, nextBatch string) {}
+// SaveNextBatch saves the mapping in-memory.
+func (s *InMemoryNextBatchStore) SaveNextBatch(userID, nextBatch string) {
+	s.UserToNextBatch[userID] = nextBatch
+}
 
-// Load does nothing
-func (s NopNextBatchStore) Load(userID string) string { return "" }
+// LoadNextBatch loads an existing mapping. Returns an empty string if not found
+func (s *InMemoryNextBatchStore) LoadNextBatch(userID string) string {
+	return s.UserToNextBatch[userID]
+}
 
 // FilterStorer controls loading/saving of filter IDs for users
 type FilterStorer interface {
-	// Save a filter ID for a given user. Best effort.
-	Save(userID, filterID string)
-	// Load a filter ID for a given user. Return an empty string if no token exists.
-	Load(userID string) string
+	// SaveFilter saves a filter ID for a given user. Best effort.
+	SaveFilter(userID, filterID string)
+	// LoadFilter loads a filter ID for a given user. Return an empty string if no token exists.
+	LoadFilter(userID string) string
+	// GetFilterJSON for the given user ID.
+	GetFilterJSON(userID string) json.RawMessage
 }
 
-// NopFilterStore does not load or save filter IDs.
-type NopFilterStore struct{}
+// InMemoryFilterStore stores filter IDs in memory. It always returns the filter JSON given in the struct.
+type InMemoryFilterStore struct {
+	Filter       json.RawMessage
+	UserToFilter map[string]string
+}
 
-// Save does nothing
-func (s NopFilterStore) Save(userID, filterID string) {}
+// SaveFilter saves the user->filter ID mapping in memory
+func (s *InMemoryFilterStore) SaveFilter(userID, filterID string) {
+	s.UserToFilter[userID] = filterID
+}
 
-// Load does nothing
-func (s NopFilterStore) Load(userID string) string { return "" }
+// LoadFilter loads a previously saved user->filter ID mapping from memory. Returns the empty string if not found.
+func (s *InMemoryFilterStore) LoadFilter(userID string) string {
+	return s.UserToFilter[userID]
+}
+
+// GetFilterJSON returns InMemoryFilterStore.Filter
+func (s *InMemoryFilterStore) GetFilterJSON(userID string) json.RawMessage {
+	return s.Filter
+}