diff --git a/src/main/java/edu/mills/cs180a/wordui/FXMLController.java b/src/main/java/edu/mills/cs180a/wordui/FXMLController.java
index 849b53c..0105e8c 100644
--- a/src/main/java/edu/mills/cs180a/wordui/FXMLController.java
+++ b/src/main/java/edu/mills/cs180a/wordui/FXMLController.java
@@ -126,8 +126,13 @@ private void configureButtons() {
                         .or(wordTextField.textProperty().isEmpty())
                         .or(definitionTextArea.textProperty().isEmpty()));
 
-        // TODO: Disable the Create button if an existing entry is selected or any
+        // Disable the Create button if an existing entry is selected or any
         // field is empty or invalid.
+        createButton.disableProperty()
+                .bind(listView.getSelectionModel().selectedItemProperty().isNotNull()
+                        .or(freqValidProperty.not())
+                        .or(wordTextField.textProperty().isEmpty())
+                        .or(definitionTextArea.textProperty().isEmpty()));
     }
 
     // A frequency is valid if it is an integer and is at least 0.