To study the influence of previous or present hepatitis B virus (HBV) infection on HIV disease progression. A prospective study of HIV-positive individuals from HIV diagnosis to diagnosis of AIDS or to the end of the follow-up period on 1 January 1991. Mean follow-up time was 62 months. The study population was recruited from a primary health-care clinic for homosexual men and followed by linkage to the National AIDS Registry. Of 876 individuals who were tested for HIV, 80 were HIV-positive and included for study. Two individuals were lost to follow-up. Differences in progression rates to AIDS according to HBV status at study entry. The adjusted relative risk of progression to AIDS for the 48 subjects who were HBV-antibody-positive at study entry was 3.6 [95% confidence interval (CI), 1.3-10.1]. A high frequency of receptive anal intercourse was also associated with more rapid HIV disease progression; adjusted relative risk 2.6 (95% CI, 1.1-5.9). Our results suggest that presence of HBV antibodies is associated with more rapid HIV-disease progression.