In-depth interviews with 27 individuals infected with syphilis in a recent UK outbreak (out of a total of 58 diagnosed between May 1999 and August 2000 in three city hospitals) were carried out to examine behaviour and attitudes. Most (23/27) participants were homosexual men, seven of whom were HIV positive. Between them, the 23 gay men had 1,494 different contacts in the twelve months prior to their awareness of having syphilis, but only 10% of these contacts could be named. While oral sex (usually unprotected) was the most prevalent behaviour (median = 30 partners per year), only 39% perceived unprotected oral sex as a syphilis risk (c.f. 70% for anal sex). Many gay men (61%) used gamma hydroxybutyrate (GHB) during sex as an aphrodisiac. This syphilis-infected subset of the population had high levels of unprotected and anonymous sex, which brings into question the usefulness of contact tracing to control syphilis outbreaks. The majority of partners were casual oral sex partners. More awareness is urgently needed around syphilis symptoms and risks, and risks of using drugs to reduce sexual inhibitions.