Objective To compare the prevalence of condom use and its associated factors within commercial and casual sex relationships between heterosexual men who seek sex online and those who frequent brothels in Singapore.

Methods A survey was conducted between 2011 and 2012 among Singaporean heterosexual men aged 21–70 years who reported engaging in sexual intercourse with commercial or casual partners in the past year. Men seeking sex online (n=304) were recruited from the two most frequented local internet sex forums. Men frequenting brothels (n=297, 97% response rate) were recruited from a stratified cluster random sample of licensed brothels.

Results Compared with men frequenting brothels, men seeking sex online reported significantly higher rates of oral and anal sex and sexually transmitted diseases but lower condom use for oral sex with commercial (16.5% vs 56.6%) and casual partners (21.2% vs 35.3%). In multivariate analyses, the online group showed that partner request for condom use was strongly associated with condom use for vaginal sex (adjusted ORs >3.0) but not with condom use for oral sex with both casual and commercial sex partners. The perceived risk of getting HIV from a partner was also associated with condom use for vaginal sex with commercial and casual partners; and for oral sex with casual partners. In contrast, condom use for oral and vaginal sex with both partners in the brothel group was only associated with partner request for condom use.

Conclusions Men seeking sex online should receive sexually transmitted infection (STI)/HIV prevention interventions that deal with the factors associated with condom use.