This thesis presents an object-oriented visual simulator for the Visual Simulation Environment (VSE). VSE allows graphical model definition and provides an object-oriented Visual Simulation Language (VSL) for specifying model logic. The Visual Simulator executes VSE models and displays the visual representation of the execution. It provides a class library used by modelers' VSL logic specification, and lets users collect statistics. Four major requirements of a visual simulator for the VSE have been identified. The simulator needs to support the object-oriented approach used in the VSE, support hierarchically defined dynamic objects, let modelers view model behavior graphically, and allow modelers to easily navigate the modeL The Visual Simulator satisfies these requirements. It fully supports the object-oriented approach used throughout the VSE by providing an object-oriented class library through which modelers access simulator features. It also provides support for hierarchically defined dynamic objects. The Visual Simulator helps users understand the structure and behavior of VSE models by providing easy viewing and navigation among model components, and by allowing inspection of object attributes. / Master of Science