Summary

The Multicenter AIDS Cohort Study (MACS) is an ongoing prospective study of the natural and treated histories of HIV-1 infection in homosexual and bisexual men conducted by sites located in Baltimore, Chicago, Pittsburgh and Los Angeles. A total of 6,972 men have been enrolled. From April 1984 through March 1985, 4954 men were enrolled; an additional 668 men were enrolled from April 1987 through September 1991. A third enrollment of 1350 men took place between October 2001 and August 2003. This third cohort augments research efforts in the long term benefits and adverse effects of therapy.