Timeline: Twenty-Five Years Later

It began with observations of a pattern of unusual illnesses in homosexual men who'd had no contact with each other. Their observation created a frame on which the edifice of AIDS, or acquired immune deficiency syndrome, knowledge could be built, piece by piece.

1981: First Report of AIDS (PDF)

1986: AID's First Five Years The "unusual" cluster had grown to an epidemic of more than 21,000 victims of acquired immune deficiency syndrome across the United States, more than half of whom had already died.

1991: AIDS Epidemic Shifting to Poor and Dispossessed Ten years after the first reported case, only half of all new AIDS cases still involved gay men. The epidemic was now moving most rapidly and most devastatingly among intravenous drug users and minorities. It was also becoming an epidemic of women and children, of the poor and dispossessed, of blacks and Hispanics, of Harlem and Watts.

1997: In this five-part series Fifteen years after AIDS entered our vocabulary, the Post sketched a picture of a new world of AIDS.

On the front line The new treatments are expensive and complicated, making it difficult for people on the fringe of society -- the homeless and drug addicts -- who make up a growing part of the AIDS epidemic.

Stopping the virus The nation's HIV prevention efforts have fractured into locally designed and implemented programs that vary widely.

The hunt for a vaccine After years of frustration and disappointment, cautious optimism is emerging among researchers trying to develop an AIDS vaccine, the ultimate weapon against the epidemic.

Despair in the Third World While new treatments have brought hope to the United States and other developed countries, the drugs are costly and complex, making them impractical in developing countries, where the epidemic continues to rage most fiercely.

2001: The Emergence of a Deadly Disease Michael S. Gottlieb recalls the day he discovered AIDS.

2006: 25 Years Later: Complete Coverage