diff --git a/accessible/clipboard.service.js b/accessible/clipboard.service.js
index eb8c0896d..035939104 100644
--- a/accessible/clipboard.service.js
+++ b/accessible/clipboard.service.js
@@ -111,5 +111,7 @@ blocklyApp.ClipboardService = ng.core
             Blockly.Msg.PASTED_BLOCK_TO_MARKED_SPOT_MSG +
             reconstitutedBlock.toString());
       }
+
+      this.markedConnection_ = null;
     }
   });
diff --git a/accessible/tree.service.js b/accessible/tree.service.js
index d9c0784fa..2387de9ae 100644
--- a/accessible/tree.service.js
+++ b/accessible/tree.service.js
@@ -117,9 +117,10 @@ blocklyApp.TreeService = ng.core
     },
     // Runs the given function while preserving the focus and active descendant
     // for the given tree.
-    runWhilePreservingFocus: function(func, treeId) {
-      var activeDescId = this.getActiveDescId(treeId);
-      this.unmarkActiveDesc_(activeDescId);
+    runWhilePreservingFocus: function(func, treeId, optionalNewActiveDescId) {
+      var oldDescId = this.getActiveDescId(treeId);
+      var newDescId = optionalNewActiveDescId || oldDescId;
+      this.unmarkActiveDesc_(oldDescId);
       func();
 
       // The timeout is needed in order to give the DOM time to stabilize
@@ -127,8 +128,8 @@ blocklyApp.TreeService = ng.core
       // pasteAbove().
       var that = this;
       setTimeout(function() {
-        that.markActiveDesc_(activeDescId);
-        that.activeDescendantIds_[treeId] = activeDescId;
+        that.markActiveDesc_(newDescId);
+        that.activeDescendantIds_[treeId] = newDescId;
         document.getElementById(treeId).focus();
       }, 0);
     },
@@ -153,11 +154,43 @@ blocklyApp.TreeService = ng.core
     isButtonOrFieldNode_: function(node) {
       return ['BUTTON', 'INPUT'].indexOf(node.tagName) != -1;
     },
+    getNextActiveDescWhenBlockIsDeleted: function(blockRootNode) {
+      // Go up a level, if possible.
+      var nextNode = blockRootNode.parentNode;
+      while (nextNode && nextNode.tagName != 'LI') {
+        nextNode = nextNode.parentNode;
+      }
+      if (nextNode) {
+        return nextNode;
+      }
+
+      // Otherwise, go to the next sibling.
+      var nextSibling = this.getNextSibling(blockRootNode);
+      if (nextSibling) {
+        return nextSibling;
+      }
+
+      // Otherwise, go to the previous sibling.
+      var previousSibling = this.getPreviousSibling(blockRootNode);
+      if (previousSibling) {
+        return previousSibling;
+      }
+
+      // Otherwise, this is a top-level isolated block, which means that
+      // something's gone wrong and this function should not have been called
+      // in the first place.
+      console.error('Could not handle deletion of block.' + blockRootNode);
+    },
     onKeypress: function(e, tree) {
       var treeId = tree.id;
       var activeDesc = document.getElementById(this.getActiveDescId(treeId));
       if (!activeDesc) {
-        console.log('ERROR: no active descendant for current tree.');
+        console.error('ERROR: no active descendant for current tree.');
+        // TODO(sll): This just gives the focus somewhere to go in the event
+        // of an error, but we need to generalize this to other trees (both
+        // within and outside the workspace).
+        this.setActiveDesc(
+            blocklyApp.workspace.topBlocks_[0].id + 'blockSummary', treeId);
         return;
       }
 
diff --git a/accessible/workspace-tree.component.js b/accessible/workspace-tree.component.js
index 48ecd2c14..98ef4d775 100644
--- a/accessible/workspace-tree.component.js
+++ b/accessible/workspace-tree.component.js
@@ -168,7 +168,7 @@ blocklyApp.WorkspaceTreeComponent = ng.core
       var elementsNeedingIds = this.getElementsNeedingIds_();
 
       this.idMap = {}
-      this.idMap['parentList'] = this.utilsService.generateUniqueId();
+      this.idMap['parentList'] = this.block.id + 'parent';
       for (var i = 0; i < elementsNeedingIds.length; i++) {
         this.idMap[elementsNeedingIds[i]] =
             this.block.id + elementsNeedingIds[i];
@@ -198,10 +198,15 @@ blocklyApp.WorkspaceTreeComponent = ng.core
     isCompatibleWithClipboard: function(connection) {
       return this.clipboardService.isCompatibleWithClipboard(connection);
     },
-    isTopLevelBlock: function(block) {
-      return blocklyApp.workspace.topBlocks_.some(function(topBlock) {
-        return topBlock.id == block.id;
-      });
+    isIsolatedTopLevelBlock: function(block) {
+      // Returns whether the given block is at the top level, and has no
+      // siblings.
+      return Boolean(
+          !block.nextConnection.targetConnection &&
+          !block.previousConnection.targetConnection &&
+          blocklyApp.workspace.topBlocks_.some(function(topBlock) {
+            return topBlock.id == block.id;
+          }));
     },
     generateAriaLabelledByAttr: function(mainLabel, secondLabel, isDisabled) {
       return this.utilsService.generateAriaLabelledByAttr(
@@ -219,40 +224,45 @@ blocklyApp.WorkspaceTreeComponent = ng.core
         that.clipboardService.pasteFromClipboard(block.nextConnection);
       }, this.tree.id);
     },
-    cutToClipboard: function(block) {
-      if (this.isTopLevelBlock(block)) {
-        nextNodeToFocusOn = this.treeService.getNodeToFocusOnWhenTreeIsDeleted(
-            this.tree.id);
-        this.clipboardService.cut(block);
+    getRootNode: function() {
+      // Gets the root HTML node for this component.
+      return document.getElementById(this.idMap['parentList']);
+    },
+    removeBlockAndSetFocus_: function(block, deleteBlockFunc) {
+      // This method runs the given function and then does one of two things:
+      // - If the block is an isolated top-level block, it shifts the tree
+      //   focus.
+      // - Otherwise, it sets the correct new active desc for the current tree.
+      if (this.isIsolatedTopLevelBlock(block)) {
+        var nextNodeToFocusOn =
+            this.treeService.getNodeToFocusOnWhenTreeIsDeleted(this.tree.id);
+        deleteBlockFunc();
         nextNodeToFocusOn.focus();
       } else {
-        // TODO(sll): Change the active descendant of the tree.
-        this.clipboardService.cut(block);
+        var nextActiveDesc =
+            this.treeService.getNextActiveDescWhenBlockIsDeleted(
+                this.getRootNode());
+        this.treeService.runWhilePreservingFocus(
+            deleteBlockFunc, this.tree.id, nextActiveDesc.id);
       }
     },
+    cutToClipboard: function(block) {
+      var that = this;
+      this.removeBlockAndSetFocus_(block, function() {
+        that.clipboardService.cut(block);
+      });
+    },
     deleteBlock: function(block) {
-      if (this.isTopLevelBlock(block)) {
-        nextNodeToFocusOn = this.treeService.getNodeToFocusOnWhenTreeIsDeleted(
-            this.tree.id);
+      this.removeBlockAndSetFocus_(block, function() {
         block.dispose(true);
-        nextNodeToFocusOn.focus();
-      } else {
-        // TODO(sll): Change the active descendant of the tree.
-        block.dispose(true);
-      }
+      });
     },
     sendToMarkedSpot: function(block) {
       this.clipboardService.pasteToMarkedConnection(block, false);
 
-      if (this.isTopLevelBlock(block)) {
-        nextNodeToFocusOn = this.treeService.getNodeToFocusOnWhenTreeIsDeleted(
-            this.tree.id);
+      this.removeBlockAndSetFocus_(block, function() {
         block.dispose(true);
-        nextNodeToFocusOn.focus();
-      } else {
-        // TODO(sll): Change the active descendant of the tree.
-        block.dispose(true);
-      }
+      });
 
       alert('Block moved to marked spot: ' + block.toString());
     }