The Russian HIV epidemic is primarily fuelled by injection drug use, but heterosexual spread may be playing an increasing role in transmission. Government-funded AIDS clinics provide most HIV treatment in Russia, and represent an important contact point between the medical community and infected population. Little is known about the population actively seeking HIV treatment. To describe demographics, perceived mode of acquisition and serostatus disclosure practices of HIV-infected individuals seeking treatment in St Petersburg, Russia, we conducted a cross-sectional study of 204 HIV-infected patients presenting to the St Petersburg City AIDS Center between May and June 2007. Mean age of respondents was 28 years old, 51% were women and two-thirds (67%) reported a history of injection drug use. Men were more likely to report injection (62% versus 45%) while women were more likely to identify sexual transmission (45% versus 32%) as their perceived infection route. Predictors of serostatus disclosure were female gender, married status and higher education. Women represent half of all patients seeking HIV treatment in St Petersburg, and are more likely than men to have disclosed their HIV-positive serostatus to sexual partners. While this population may not represent the burden of HIV disease in Russia, it is an important target group for secondary prevention.