OBJECTIVE: The objective of this study was to determine the prevalence, incidence, and risk factors for genital and anal warts in HIV-negative homosexual men in Sydney. STUDY DESIGN: The authors conducted a prospective cohort study. Participants were asked whether they had had genital and anal warts at each interview. Details of lifetime sexual contacts and sexual behaviors in the last 6 months were collected. RESULTS: Among 1,427 men recruited, 8.9% and 19.6% reported a history of genital and anal warts at baseline, respectively. Incidence rates for genital and anal warts were 0.94 and 1.92 per 100 person-years, respectively. In multivariate analysis, both incident genital and anal warts were associated with younger age. In addition, incident genital warts was associated with insertive fingering (P trend = 0.018), whereas incident anal warts was associated with insertive fingering (P trend = 0.007) and insertive fisting (P trend = 0.039). CONCLUSIONS: Anal warts were twice as common as genital warts. Fingering and other manual sexual practices may be an important transmission route for both.