Since we make MPICH publicly available by ftp, we do not have precise counts on the number of users. It is downloaded about 300 times per month from our ftp site, ftp.mcs.anl.gov, which is also mirrored at Mississippi State, ftp.erc.msstate.edu. Judging from the bug reports and subscriptions to the mpi-users mailing list, we estimate that between five hundred and one thousand people are currently active in their use of MPICH.