Our objective was to determine factors associated with sexual problems in a sample of HIV-seropositive gay male clinic patients. Using a cross-sectional survey design a volunteer sample of 78 outpatient HIV-seropositive gay male service users completed a self-report questionnaire. This examined sexual problems, their perceived causes and associated factors including demographics, health status, sexual behaviour, self-justifications for sexual risk-taking and mood state (Hospital Anxiety and Depression Scale). Fifty (69%) of 78 HIV-positive gay men reported one or more sexual problems. Erectile dysfunction (ED) was reported by 38% rising to 51% in the context of trying to use condoms. Loss of interest in sex was reported by 41% and 24% experienced delayed ejaculation. The presence of sexual problems affected condom use in that 33 (90%) of the 37 gay men who had ED associated with condom use were inconsistent condom users in insertive sex compared to 28% of those not having this type of ED ( P < 0.001). The presence of ED did not reduce the frequency of anal intercourse but those with ED associated with condoms were significantly more likely to have had receptive anal sex in the past three months (62%) compared to men without ED with condoms (38%) ( P = 0.05). Risk cognitions such as wanting to lose oneself in sex, leaving responsibility for condom use to the active partner and perceptions that condoms interfere with pleasure were significantly more likely to be endorsed by those who report ED with condoms. Other factors associated with sexual problems included low T-cell counts (i.e. < 200). Psychological explanations were the most frequently cited causes of sexual problems, whether alone or in interaction with HIV disease itself, and combination therapy. A high incidence of sexual problems was found amongst this sample of HIV-positive gay men. Untreated sexual dysfunctions may contribute to sexual risk-taking and therefore HIV clinics need to address both issues. Further research is required to better understand the role of psychological factors, HIV disease itself and combination therapy in the incidence and treatment of sexual problems.