ClustDB is a tool for the identification of perfect matches in large sets of sequences. It is faster and can handle at least 8 times more data than VMATCH, the most memory efficient exact program currently available. Still ClustDB needs about four hours to compare all Human ESTs. We therefore present a distributed and parallel implementation of ClustDB to reduce the execution time. It uses a message-passing library called MPI and runs on distributed workstation clusters with significant runtime savings. MPI-ClustDB is written in ANSI C and freely available on request from the authors.