March 17, 1999 The Multicenter AIDS Cohort (MACS), a four-institution, 15-year research project that has tracked the occurrence and consequences of human immunodefiency virus (HIV) in the lives of a group of 5,000 homosexual and bisexual men since the early nineteen-eighties, will celebrate its fifteenth anniversary on March 31, 1999. Because AIDS in the early eighties was found largely in homosexual men, the MACS was set up to gather epidemiological evidence and to try and understand the full spectrum of the AIDS related diseases. More than 5,000 volunteers came forward to join the study. Of the cohort in Baltimore, 109 have come to every clinic visit for the past 15 years. More than 600 articles have been generated from the MACS research ranging from the role of CD4 lymphocyte counts and viral load in predicting AIDS, to average incubation time, to the genetics of AIDS - why some people handle the virus so much better than others. Over the years the MACS has provided critical data about early events in the course of HIV infection and about conversion to AIDS. The study also looked at factors that might be involved in transmitting the infection and helped identify the most important ones. Finally, the MACS has built up a large repository of biologic specimens with detailed epidemiologic data for investigators, which have been used in a wide variety of studies by AIDS researchers nationwide. The MACS sites are the Johns Hopkins School of Public Health in Baltimore, Maryland; Northwestern University Medical School in Chicago, Illinois; University of California Schools of Public Health and Medicine in Los Angeles; and University of Pittsburgh Graduate School of Public Health in Pittsburgh, Pennsylvania. Please contact the Office of Communication at the Johns Hopkins School of Public Health if you would like to talk to study volunteers or researchers. Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham @ 410-955-6878 or paffairs@jhsph.edu. | 
