Objectives: To examine aggregate changes in homosexual HIV risk taking among gay men attending the Gay Pride festival in the United Kingdom over a three year period during which HIV prevention activity targeted at this population increased considerably. Design: Three cross-sectional self-completion questionnaires at yearly intervals asking identical questions on sexual behaviour in the preceding year. Setting: Lesbian and Gay Pride festival held in London, June 1993, 1994 and 1995. Participants: Men attending the festival who were UK resident, had ever had sex with another man and who were willing to fill out a questionnaire (N= 1620, 1753 and 1168 in 1993, 1994, and 1995, respectively). Main outcome measures: Self reported numbers of sexual partners, sexual partners with whom ano- penile intercourse occurred and sexual partners with whom ano-penile intercourse occurred without a condom. Results: Over the three year period there were no changes in the proportion of men engaging in any of the sexual behaviour measures. At each cross-section, one in three men (514 out of 1566, 511 out of 1612, 351 out of 1059) had engaged in AI without a condom with at least one male partner in the preceding year and one in ten (162 out of 1566, 156 out of 1612, 103 out of 1059) had done so with more than one male partner. Conclusion: Despite an increase in prevention work targeted at this population, aggregate levels of sexual risk taking have remained very stable. A reassessment of the efficacy of current HIV prevention messages and methods with this population is urgently required.