In this paper we present a new parallel clustering algorithm based on the extended star clustering method. This algorithm can be used for example to cluster massive data sets of documents on distributed memory multiprocessors. The algorithm exploits the inherent data-parallelism in the extended star clustering algorithm. We implemented our algorithm on a cluster of personal computers connected through a Myrinet network. The code is portable to different architectures and it uses the MPI message-passing library. The experimental results show that the parallel algorithm clearly improves its sequential version with large data sets. We show that the speedup of our algorithm approaches the optimal as the number of objects increases.