Visualization is a useful tool in many areas of computer scil ence education. This paper describes the use of visualization in the introduction of object-oriented concepts. A Java application has been developed that allpws the user' to interact with a visualiza.tion of any Java class through the instantiation of objects, the movement of those objects around the class environment, and the activation of class methods. The user may also move conveniently between classes in this visualization.This Object Visualizer is useful for classroom demonstration, individual student use in the laboratory,. and class debugging and testing.