During the 1990s, cases of infectious syphilis were uncommon in Wales. In 2002, an outbreak occurred in a sexual network of men who have sex with men (MSM) attending a sauna. A multidisciplinary outbreak control team was convened to raise awareness of the outbreak among MSM and health professionals, assess the extent of outbreak, and initiate surveillance measures. It is likely that early intensive control efforts dampened the epidemic curve. However, since 2006 the number of cases has increased steadily to a peak of four cases per 100,000 population in 2008. The majority of cases continue to occur in MSM (81% in 2009) and in those attending genitourinary (GU) medicine clinics in south east Wales (76%). Traditional sexual networks such as saunas, bars/clubs and cruising grounds remain frequently reported, but Internet-based networks are assuming increasing importance. Public health interventions have been sustained, using traditional partner notification, health promotion initiatives, and more innovative Internet network tracing methods.