ATM networking promises to usher in a new era in network technology by providing an integrated network that can be used to transmit voice, video, image, interactive data and bulk data at very high speeds. An ATM switch enables the routing of data packets through the ATM network. In this paper, we describe the development of a behavioral model for an ATM switch using SpecCharts. The SpecCharts language, developed at the University of California, Irvine, is based on the conceptual model of a system as a Program State Machine, and is defined as an extension of VHDL. SpecCharts was found to be very well suited suited for expressing the functionality of the system, as it provides support for behavioral hierarchy, state transitions and exception handling, features not supported by VHDL. The SpecCharts model was translated automatically to VHDL. A behavioral VHDL model was created for an ATM traffic source. A testbench was developed that incorporates the generated ATM switch VHDL model and the traffic source model. The switch description was verified by simulation using the Vantage VHDL simulator.