The Y-maze can be used to assess short term memory in mice. Spontaneous alternation, a measure of spatial working memory, can be assessed by allowing mice to explore all three arms of the maze and is driven by an innate curiosity of rodents to explore previously unvisited areas. A mouse with intact working memory, and hence intact prefrontal cortical functions, will remember the arms previously visited and show a tendency to enter a less recently visited arm. Spatial reference memory, which is underlined by the hippocampus, can also be tested by placing the test mice into the Y-maze with one arm closed off during training. After an inter-trial interval of for example 1 h, the mouse should remember which arm it has not explored previously and should visit this arm more often. This chapter describes the pre-test conditions, the materials required and the protocol for conducting and interpreting the results of these two related tests.