This article presents a definition of HIV disease as a four-stage process. The Sickness Impact Profile (SIP) (Bergner, Bobbitt, Carter, & Gilson, 1981) was used to measure behavioral dysfunction in a sample of 15 persons with Stage 3 or Stage 4 (symptomatic) HIV disease. The areas of work, leisure, cognitive behavior, and emotional behavior were found to be, on the average, most affected by HIV disease. A diagnosis of AIDS does not affect the severity of dysfunction. Functional deficits that are experienced for longer periods of time affect several behavioral categories on the SIP as well as on the overall SIP score.