This is the first paper to forecast the cost of medical care for all people with the human immunodeficiency virus (HIV). Previous studies have concentrated on the cost of treating people with AIDS (PWAs). It is estimated that the average cost of treating a person with HIV without AIDS is $5,150 per year, and that the average cost of treating a PWA is $32,000 per year ($24,000 for inpatient hospital care and $8,000 for other services). The lifetime cost of medical care for a PWA is calculated to be $85,333. This is higher than many previous estimates of lifetime costs due to increased longevity and the diffusion of costly outpatient drugs. The cost of treating all people with HIV in 1991 is forecast to be $5.8 billion. Of this amount, it is estimated that $1.4 billion will be spent on people with HIV without AIDS, and the remaining $4.4 billion on PWAs. It is forecast that the cost of treating all people with HIV will increase 21% each year between 1991 and 1994, and that $10.4 billion will be spent on treating all people with HIV in 1994.