OBJECTIVE: We investigated factors associated with unprotected sex in regular partnerships among homosexual men living with HIV. METHOD: We used data from a French national representative sample of people living with HIV (ANRS-EN12-VESPA survey). This analysis included men in a regular partnership with another man for at least twelve months. Unprotected sex was defined as reporting at least one episode of sexual intercourse without a condom with this regular partner in the previous 12 months. Separate analyses were conducted in sero-nonconcordant couples and in HIV-positive seroconcordant couples. RESULTS: 285 and 193 homosexual men respectively reported a regular sero-nonconcordant and seroconcordant partner. Unprotected sex was reported by a higher number of respondents within seroconcordant (46.7%) than within sero-nonconcordant couples (15.6%). In both seroconcordant and sero-nonconcordant partnerships, unprotected sex was significantly more frequent when episodes of unprotected sex with casual partners were reported. In seroconcordant couples, those who had more than four casual partners were also more likely to practise unprotected sex with their regular partner. Among sero-nonconcordant couples, binge drinking and absence of disclosure of one's HIV-positive status to the partner were also independently associated with unprotected sex. CONCLUSIONS: A limited number of sero-nonconcordant homosexual couples persist in reporting risky sexual behaviour. Prevention messages should encourage communication and HIV disclosure. The relationship between unprotected sex with both casual and regular partners also calls attention about the underlying psycho-social and interactional factors that may influence sexual behaviours of people living with HIV in regular relationships, independently of the status of the partner.