Persons using assistive technology might not be able to fully access information in this file. For assistance, please send e-mail to: mmwrq@cdc.gov. Type 508 Accommodation and the title of the report in the subject line of e-mail. First Report of AIDS Twenty years ago, on June 5, 1981, MMWR published a report of five cases of Pneumocystis carinii pneumonia (PCP) among previously healthy young men in Los Angeles (1). All of the men were described as "homosexuals"; two had died. Local clinicians and the Epidemic Intelligence Service (EIS) Officer stationed at the Los Angeles County Department of Public Health, prepared the report and submitted it for MMWR publication in early May 1981. Before publication, MMWR editorial staff sent the submission to CDC experts in parasitic and sexually transmitted diseases. The editorial note that accompanied the published report stated that the case histories suggested a "cellular-immune dysfunction related to a common exposure" and a "disease acquired through sexual contact." The report prompted additional case reports from New York City, San Francisco, and other cities. At about the same time, CDC's investigation drug unit, the sole distributor of pentamidine, the therapy for PCP, began to receive requests for the drug from physicians also to treat young men. In June 1981, CDC developed an investigative team to identify risk factors and to develop a case definition for national surveillance. Within 18 months, epidemiologists conducted studies and prepared MMWR reports that identified all of the major risks factors for acquired immnodeficiency syndrome (AIDS). In March 1983, CDC issued recommendations for prevention of sexual, drug-related, and occupational transmission based on these early epidemiologic studies and before the cause of the new, unexplained illness was known. MMWR has published more than 400 reports about human immunodeficiency virus (HIV) and AIDS and remains a primary source of information about the epidemiology, surveillance, prevention, care, and treatment of HIV and AIDS. This anniversary issue provides new reports on the epidemiologic features and impact of HIV/AIDS on communities in the United States and in other countries. A compilation of notable MMWR reports on HIV and AIDS is available at http://www.cdc.gov/mmwr/hiv_aids20.html. A video that includes interviews with participants in these first AIDS investigations and reports and a video summary of each report in this issue is available at http://www.cdc.gov/mmwr. Reference CDC. Pneumocystis pneumonia --- Los Angeles. MMWR 1981;30:250--2. Disclaimer All MMWR HTML versions of articles are electronic conversions from ASCII text into HTML. This conversion may have resulted in character translation or format errors in the HTML version. Users should not rely on this HTML document, but are referred to the electronic PDF version and/or the original MMWR paper copy for the official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices. **Questions or messages regarding errors in formatting should be addressed to mmwrq@cdc.gov. Page converted: 6/8/2001