Abstract. In this paper we study an heuristic approach, based on parallelism, to estimate the Diameter-Constrained Reliability (DCR) of a given undirected probabilistic graph G = (V, E), with two terminal nodes s and t, a given diameter bound D, and where edges are assigned independent probabilities of failure (node are assumed to be perfect). Since exact methods to evaluate the DCR are computationally expensive (i.e., NP-hard), we propose to implement a Monte Carlo (M C) method based upon MPI parallel processing to estimate the reliability. We conduct computational tests on several topologies while considering different factors such as number of cluster nodes utilized, number of trials performed by the cluster nodes, different ranges generated by random number functions, and then we determine how these factors affect the estimation of the DCR.