diff --git a/chrome/content/zotero/xpcom/collectionTreeView.js b/chrome/content/zotero/xpcom/collectionTreeView.js
index e4db3c24f..f79a2f84c 100644
--- a/chrome/content/zotero/xpcom/collectionTreeView.js
+++ b/chrome/content/zotero/xpcom/collectionTreeView.js
@@ -647,16 +647,22 @@ Zotero.CollectionTreeView.prototype.drop = function(row, orient)
 	}
 	else if (dataType == 'zotero/item') {
 		var ids = data.data.split(',');
-		var targetCollection = this._getItemAtRow(row).ref;
-		for each(var id in ids)
-		{
-			var item = Zotero.Items.get(id);
+		if (ids.length < 1) {
+			return;
+		}
+		
+		var toAdd = [];
+		for (var i=0; i<ids.length; i++) {
+			var item = Zotero.Items.get(ids[i]);
 			// Only accept top-level items
-			if (item.isRegularItem() || !item.getSource())
-			{
-				targetCollection.addItem(id);
+			if (item.isRegularItem() || !item.getSource()) {
+				toAdd.push(ids[i]);
 			}
 		}
+		
+		if (toAdd.length > 0) {
+			this._getItemAtRow(row).ref.addItems(toAdd);
+		}
 	}
 	else if (dataType == 'text/x-moz-url') {
 		var url = data.data.split("\n")[0];
diff --git a/chrome/content/zotero/xpcom/data_access.js b/chrome/content/zotero/xpcom/data_access.js
index 9b11a9520..fe3032dca 100644
--- a/chrome/content/zotero/xpcom/data_access.js
+++ b/chrome/content/zotero/xpcom/data_access.js
@@ -3013,6 +3013,22 @@ Zotero.Collection.prototype.addItem = function(itemID){
 }
 
 
+/**
+ * Add multiple items to the collection in batch
+ */
+Zotero.Collection.prototype.addItems = function(itemIDs) {
+	if (!itemIDs || !itemIDs.length) {
+		return;
+	}
+	
+	Zotero.DB.beginTransaction();
+	for (var i=0; i<itemIDs.length; i++) {
+		this.addItem(itemIDs[i]);
+	}
+	Zotero.DB.commitTransaction();
+}
+
+
 /**
 * Remove an item from the collection (does not delete item from library)
 **/
@@ -3032,6 +3048,22 @@ Zotero.Collection.prototype.removeItem = function(itemID){
 }
 
 
+/**
+ * Remove multiple items from the collection in batch
+ * (does not delete item from library)
+ */
+Zotero.Collection.prototype.removeItems = function(itemIDs) {
+	if (!itemIDs || !itemIDs.length) {
+		return;
+	}
+	
+	Zotero.DB.beginTransaction();
+	for (var i=0; i<itemIDs.length; i++) {
+		this.removeItem(itemIDs[i]);
+	}
+	Zotero.DB.commitTransaction();
+}
+
 /**
 * Check if an item belongs to the collection
 **/
diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index dd0e70885..9ebb4ef87 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -992,9 +992,7 @@ Zotero.ItemTreeView.prototype.deleteSelection = function(eraseChildren, force)
 		Zotero.Items.erase(ids, eraseChildren);
 	}
 	else if (this._itemGroup.isCollection()) {
-		for each(var id in ids) {
-			this._itemGroup.ref.removeItem(id);
-		}
+		this._itemGroup.ref.removeItems(ids);
 	}
 	this._treebox.endUpdateBatch();
 }