Serial biannual cross-sectional assessments of HIV sexual risk indicated a consistent increase in safer sexual practices among homosexual men participating in the Chicago-Multicenter AIDS Cohort Study (MACS)/Coping and Change Study (CCS) in 1986–1988. Safer sexual practices were achieved by avoidance of anal sex and less often by consistent use of condoms. Longitudinal patterns of variability in individual behavior were also assessed. After 1 year of follow-up, 53% of the participants maintained safer practices in receptive anal sex, 6% maintained unsafe practices, while 31% relapsed at least once. After 2 years, 45% maintained safer practices, 3% maintained unsafe practices and 47% relapsed at least once. Similar trends were observed in insertive anal sex.