diff --git a/src/ch/zhaw/ads/AVLSearchTree.java b/src/ch/zhaw/ads/AVLSearchTree.java
index 6a6441f..ad649f2 100644
--- a/src/ch/zhaw/ads/AVLSearchTree.java
+++ b/src/ch/zhaw/ads/AVLSearchTree.java
@@ -8,7 +8,11 @@ package ch.zhaw.ads;
  */
 public class AVLSearchTree<T extends Comparable<T>> extends SortedBinaryTree<T> {
     private boolean balanced(TreeNode<T> node) {
-        // TODO Implement (6.4)
+        if(Math.abs(calcHeight(node.right) - calcHeight(node.left)) > 1
+        || (node.right != null && !balanced(node.right))
+        || (node.left != null && !balanced(node.left))){
+            return false;
+        }
         return true;
     }