A fundamental issue in the automated analysis of communicating systems is the efficient generation of the reachable state space. Since it is not possible to generate all the reachable states of a system with an infinite number of states, we need a way to combine sets of states. In this paper, we describe communicating state machines with data variables, which we use to specify concurrent systems. We then present an algorithm that constructs the minimal reachability graph of a labeled transition system with infinite data values. Our algorithm clusters a set of states that are bisimilar into an equivalent class. We include an example to illustrate our algorithm and identify a set of sufficient conditions that guarantees the termination of the algorithm.