In this paper, we consider the problem of scheduling tasks with fixed small communications delays on a virtual distributed memory multiprocessor when the tasks execution times are random. This problem extends the classical PERT scheduling problem with random execution times and no communications. We first present how to efficiently build pre-schedulings for this problem. We then compute a lower bound of the average makespan of a given pre-scheduling. We finally propose a lower and an upper bound of the execution time of the best pre-scheduling.