diff --git a/dist/leaflet.markercluster-src.js b/dist/leaflet.markercluster-src.js
index c3ab1b4404..fd438b53e2 100644
--- a/dist/leaflet.markercluster-src.js
+++ b/dist/leaflet.markercluster-src.js
@@ -31,6 +31,10 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 		//Increase to increase the distance away that spiderfied markers appear from the center
 		spiderfyDistanceMultiplier: 1,
 
+		//When bulk adding layers, runs chunks at a time. Means addLayers may not add all the layers in the call, others will be loaded during setTimeouts
+		chunkedLoading: false,
+		chunkSize: 500,
+
 		//Options to pass to the L.Polygon constructor
 		polygonOptions: {}
 	},
@@ -157,52 +161,76 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 
 	//Takes an array of markers and adds them in bulk
 	addLayers: function (layersArray) {
-		var i, l, m,
-			onMap = this._map,
-			fg = this._featureGroup,
-			npg = this._nonPointGroup;
+		var fg = this._featureGroup,
+			npg = this._nonPointGroup,
+			chunkSize = this.options.chunkSize,
+			newMarkers, i, l, m;
 
-		for (i = 0, l = layersArray.length; i < l; i++) {
-			m = layersArray[i];
+		if (this._map) {
+			var start = 0;
+			var end = this.options.chunkedLoading && chunkSize < layersArray.length ? chunkSize : layersArray.length;
+			var process = L.bind(function () {
+				for (i = start; i < end; i++) {
+					m = layersArray[i];
 
-			//Not point data, can't be clustered
-			if (!m.getLatLng) {
-				npg.addLayer(m);
-				continue;
-			}
+					//Not point data, can't be clustered
+					if (!m.getLatLng) {
+						npg.addLayer(m);
+						continue;
+					}
 
-			if (this.hasLayer(m)) {
-				continue;
-			}
+					if (this.hasLayer(m)) {
+						continue;
+					}
 
-			if (!onMap) {
-				this._needsClustering.push(m);
-				continue;
-			}
+					this._addLayer(m, this._maxZoom);
 
-			this._addLayer(m, this._maxZoom);
-
-			//If we just made a cluster of size 2 then we need to remove the other marker from the map (if it is) or we never will
-			if (m.__parent) {
-				if (m.__parent.getChildCount() === 2) {
-					var markers = m.__parent.getAllChildMarkers(),
-						otherMarker = markers[0] === m ? markers[1] : markers[0];
-					fg.removeLayer(otherMarker);
+					//If we just made a cluster of size 2 then we need to remove the other marker from the map (if it is) or we never will
+					if (m.__parent) {
+						if (m.__parent.getChildCount() === 2) {
+							var markers = m.__parent.getAllChildMarkers(),
+								otherMarker = markers[0] === m ? markers[1] : markers[0];
+							fg.removeLayer(otherMarker);
+						}
+					}
 				}
-			}
-		}
 
-		if (onMap) {
-			//Update the icons of all those visible clusters that were affected
-			fg.eachLayer(function (c) {
-				if (c instanceof L.MarkerCluster && c._iconNeedsUpdate) {
-					c._updateIcon();
+				if (end === layersArray.length) {
+					//Update the icons of all those visible clusters that were affected
+					this._featureGroup.eachLayer(function (c) {
+						if (c instanceof L.MarkerCluster && c._iconNeedsUpdate) {
+							c._updateIcon();
+						}
+					});
+
+					this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+				} else {
+					start = end;
+					end = Math.min(end + chunkSize, layersArray.length);
+					setTimeout(process, 0);
 				}
-			});
+			}, this);
 
-			this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+			process();
+		} else {
+			newMarkers = [];
+			for (i = 0, l = layersArray.length; i < l; i++) {
+				m = layersArray[i];
+
+				//Not point data, can't be clustered
+				if (!m.getLatLng) {
+					npg.addLayer(m);
+					continue;
+				}
+
+				if (this.hasLayer(m)) {
+					continue;
+				}
+
+				newMarkers.push(m);
+			}
+			this._needsClustering = this._needsClustering.concat(newMarkers);
 		}
-
 		return this;
 	},
 
@@ -418,23 +446,9 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 		}
 		this._needsRemoving = [];
 
-		for (i = 0, l = this._needsClustering.length; i < l; i++) {
-			layer = this._needsClustering[i];
-
-			//If the layer doesn't have a getLatLng then we can't cluster it, so add it to our child featureGroup
-			if (!layer.getLatLng) {
-				this._featureGroup.addLayer(layer);
-				continue;
-			}
-
-
-			if (layer.__parent) {
-				continue;
-			}
-			this._addLayer(layer, this._maxZoom);
-		}
-		this._needsClustering = [];
-
+		//Remember the current zoom level and bounds
+		this._zoom = this._map.getZoom();
+		this._currentShownBounds = this._getExpandedVisibleBounds();
 
 		this._map.on('zoomend', this._zoomEnd, this);
 		this._map.on('moveend', this._moveEnd, this);
@@ -445,15 +459,10 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 
 		this._bindEvents();
 
-
 		//Actually add our markers to the map:
-
-		//Remember the current zoom level and bounds
-		this._zoom = this._map.getZoom();
-		this._currentShownBounds = this._getExpandedVisibleBounds();
-
-		//Make things appear on the map
-		this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+		l = this._needsClustering;
+		this._needsClustering = [];
+		this.addLayers(l);
 	},
 
 	//Overrides FeatureGroup.onRemove
@@ -631,7 +640,7 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 			e.layer.zoomToBounds();
 		}
 
-    // Focus the map again for keyboard users.
+		// Focus the map again for keyboard users.
 		if (e.originalEvent && e.originalEvent.keyCode === 13) {
 			map._container.focus();
 		}
diff --git a/example/marker-clustering-realworld.10000.html b/example/marker-clustering-realworld.10000.html
index 873a0f654f..462e8483ea 100644
--- a/example/marker-clustering-realworld.10000.html
+++ b/example/marker-clustering-realworld.10000.html
@@ -27,7 +27,7 @@
 			latlng = L.latLng(-37.89, 175.46);
 		var map = L.map('map', {center: latlng, zoom: 13, layers: [cloudmade]});
 
-		var markers = L.markerClusterGroup();
+		var markers = L.markerClusterGroup({ chunkedLoading: true });
 		
 		for (var i = 0; i < addressPoints.length; i++) {
 			var a = addressPoints[i];
diff --git a/example/marker-clustering-realworld.50000.html b/example/marker-clustering-realworld.50000.html
index 0f7c7e662a..ff73a8824a 100644
--- a/example/marker-clustering-realworld.50000.html
+++ b/example/marker-clustering-realworld.50000.html
@@ -18,6 +18,7 @@
 </head>
 <body>
 
+    <div id="progress"><div id="progress-bar"></div></div>
 	<div id="map"></div>
 	<span>Mouse over a cluster to see the bounds of its children and click a cluster to zoom to those bounds</span>
 	<script type="text/javascript">
@@ -28,12 +29,28 @@
 
 			var map = L.map('map', { center: latlng, zoom: 13, layers: [cloudmade] });
 
-			var markers = L.markerClusterGroup();
+			var progress = document.getElementById('progress');
+			var progressBar = document.getElementById('progress-bar');
+
+			function updateProgressBar(processed, total, elapsed, layersArray) {
+				if (elapsed > 1000) {
+					// if it takes more than a second to load, display the progress bar:
+					progress.style.display = 'block';
+					progressBar.style.width = Math.round(processed/total*100) + '%';
+				}
+
+				if (processed === total) {
+					// all markers processed - hide the progress bar:
+					progress.style.display = 'none';
+				}
+			}
+
+			var markers = L.markerClusterGroup({ chunkedLoading: true, chunkProgress: updateProgressBar });
 
 			var markerList = [];
 
 			//console.log('start creating markers: ' + window.performance.now());
-			
+
 			for (var i = 0; i < addressPoints.length; i++) {
 				var a = addressPoints[i];
 				var title = a[2];
diff --git a/example/screen.css b/example/screen.css
index ea33d34ca6..c89cba86c4 100644
--- a/example/screen.css
+++ b/example/screen.css
@@ -2,4 +2,27 @@
 	width: 800px; 
 	height: 600px; 
 	border: 1px solid #ccc;
-	}
\ No newline at end of file
+}
+
+#progress {
+    display: none;
+    position: absolute;
+    z-index: 1000;
+    left: 400px;
+    top: 300px;
+    width: 200px;
+    height: 20px;
+    margin-top: -20px;
+    margin-left: -100px;
+    background-color: #fff;
+    background-color: rgba(255, 255, 255, 0.7);
+    border-radius: 4px;
+    padding: 2px;
+}
+
+#progress-bar {
+    width: 0;
+    height: 100%;
+    background-color: #76A6FC;
+    border-radius: 4px;
+}
diff --git a/src/MarkerClusterGroup.js b/src/MarkerClusterGroup.js
index 65a8f2c495..7c0d956080 100644
--- a/src/MarkerClusterGroup.js
+++ b/src/MarkerClusterGroup.js
@@ -26,6 +26,12 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 		//Increase to increase the distance away that spiderfied markers appear from the center
 		spiderfyDistanceMultiplier: 1,
 
+		// When bulk adding layers, adds markers in chunks. Means addLayers may not add all the layers in the call, others will be loaded during setTimeouts
+		chunkedLoading: false,
+		chunkInterval: 200, // process markers for a maximum of ~ n milliseconds (then trigger the chunkProgress callback)
+		chunkDelay: 50, // at the end of each interval, give n milliseconds back to system/browser
+		chunkProgress: null, // progress callback: function(processed, total, elapsed) (e.g. for a progress indicator)
+
 		//Options to pass to the L.Polygon constructor
 		polygonOptions: {}
 	},
@@ -152,52 +158,89 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 
 	//Takes an array of markers and adds them in bulk
 	addLayers: function (layersArray) {
-		var i, l, m,
-			onMap = this._map,
-			fg = this._featureGroup,
-			npg = this._nonPointGroup;
+		var fg = this._featureGroup,
+			npg = this._nonPointGroup,
+			chunkInterval = this.options.chunkInterval,
+			chunkProgress = this.options.chunkProgress,
+			newMarkers, i, l, m;
 
-		for (i = 0, l = layersArray.length; i < l; i++) {
-			m = layersArray[i];
+		if (this._map) {
+			var offset = 0,
+				started = (new Date()).getTime();
+			var process = L.bind(function () {
+				var start = (new Date()).getTime();
+				for (; offset < layersArray.length; offset++) {
+					if (offset % 200 === 0) {
+						// every couple hundred markers, instrument the time elapsed since processing started:
+						var elapsed = (new Date()).getTime() - start;
+						if (elapsed > chunkInterval) {
+							break; // been working too hard, time to take a break :-)
+						}
+					}
 
-			//Not point data, can't be clustered
-			if (!m.getLatLng) {
-				npg.addLayer(m);
-				continue;
-			}
+					m = layersArray[offset];
 
-			if (this.hasLayer(m)) {
-				continue;
-			}
+					//Not point data, can't be clustered
+					if (!m.getLatLng) {
+						npg.addLayer(m);
+						continue;
+					}
 
-			if (!onMap) {
-				this._needsClustering.push(m);
-				continue;
-			}
+					if (this.hasLayer(m)) {
+						continue;
+					}
 
-			this._addLayer(m, this._maxZoom);
+					this._addLayer(m, this._maxZoom);
 
-			//If we just made a cluster of size 2 then we need to remove the other marker from the map (if it is) or we never will
-			if (m.__parent) {
-				if (m.__parent.getChildCount() === 2) {
-					var markers = m.__parent.getAllChildMarkers(),
-						otherMarker = markers[0] === m ? markers[1] : markers[0];
-					fg.removeLayer(otherMarker);
+					//If we just made a cluster of size 2 then we need to remove the other marker from the map (if it is) or we never will
+					if (m.__parent) {
+						if (m.__parent.getChildCount() === 2) {
+							var markers = m.__parent.getAllChildMarkers(),
+								otherMarker = markers[0] === m ? markers[1] : markers[0];
+							fg.removeLayer(otherMarker);
+						}
+					}
 				}
-			}
-		}
 
-		if (onMap) {
-			//Update the icons of all those visible clusters that were affected
-			fg.eachLayer(function (c) {
-				if (c instanceof L.MarkerCluster && c._iconNeedsUpdate) {
-					c._updateIcon();
+				if (chunkProgress) {
+					// report progress and time elapsed:
+					chunkProgress(offset, layersArray.length, (new Date()).getTime() - started);
 				}
-			});
 
-			this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+				if (offset === layersArray.length) {
+					//Update the icons of all those visible clusters that were affected
+					this._featureGroup.eachLayer(function (c) {
+						if (c instanceof L.MarkerCluster && c._iconNeedsUpdate) {
+							c._updateIcon();
+						}
+					});
+
+					this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+				} else {
+					setTimeout(process, this.options.chunkDelay);
+				}
+			}, this);
+
+			process();
+		} else {
+			newMarkers = [];
+			for (i = 0, l = layersArray.length; i < l; i++) {
+				m = layersArray[i];
+
+				//Not point data, can't be clustered
+				if (!m.getLatLng) {
+					npg.addLayer(m);
+					continue;
+				}
+
+				if (this.hasLayer(m)) {
+					continue;
+				}
+
+				newMarkers.push(m);
+			}
+			this._needsClustering = this._needsClustering.concat(newMarkers);
 		}
-
 		return this;
 	},
 
@@ -296,7 +339,7 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 	//Overrides LayerGroup.eachLayer
 	eachLayer: function (method, context) {
 		var markers = this._needsClustering.slice(),
-		    i;
+			i;
 
 		if (this._topClusterLevel) {
 			this._topClusterLevel.getAllChildMarkers(markers);
@@ -413,23 +456,9 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 		}
 		this._needsRemoving = [];
 
-		for (i = 0, l = this._needsClustering.length; i < l; i++) {
-			layer = this._needsClustering[i];
-
-			//If the layer doesn't have a getLatLng then we can't cluster it, so add it to our child featureGroup
-			if (!layer.getLatLng) {
-				this._featureGroup.addLayer(layer);
-				continue;
-			}
-
-
-			if (layer.__parent) {
-				continue;
-			}
-			this._addLayer(layer, this._maxZoom);
-		}
-		this._needsClustering = [];
-
+		//Remember the current zoom level and bounds
+		this._zoom = this._map.getZoom();
+		this._currentShownBounds = this._getExpandedVisibleBounds();
 
 		this._map.on('zoomend', this._zoomEnd, this);
 		this._map.on('moveend', this._moveEnd, this);
@@ -440,15 +469,10 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 
 		this._bindEvents();
 
-
 		//Actually add our markers to the map:
-
-		//Remember the current zoom level and bounds
-		this._zoom = this._map.getZoom();
-		this._currentShownBounds = this._getExpandedVisibleBounds();
-
-		//Make things appear on the map
-		this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
+		l = this._needsClustering;
+		this._needsClustering = [];
+		this.addLayers(l);
 	},
 
 	//Overrides FeatureGroup.onRemove
@@ -626,7 +650,7 @@ L.MarkerClusterGroup = L.FeatureGroup.extend({
 			e.layer.zoomToBounds();
 		}
 
-    // Focus the map again for keyboard users.
+		// Focus the map again for keyboard users.
 		if (e.originalEvent && e.originalEvent.keyCode === 13) {
 			map._container.focus();
 		}