Injection drug users (IDUs) are the vanguard of the human immunodeficiency virus (HIV) epidemic in Russia. We sought a non-invasive method to estimate a point prevalence of HIV, hepatitis B virus (HBV), hepatitis C virus (HCV), syphilis and risk behaviours in IDUs attending the syringe exchange programme (SEP) in St Petersburg, Russia. One hundred and one IDUs returning syringes to the St Petersburg SEP were invited to complete a questionnaire requesting demographic, knowledge, and behavioural information, and to provide their syringes for antibody testing. The median age of IDUs was 23 years. Syringe prevalences were: 10.9% for HIV, 78.2% for HCV, 15.8% for HBV, and 6.9% for syphilis. All respondents recognized drug-related risk factors for getting AIDS. Only two-thirds of subjects recognized condoms to prevent sexually transmitted infections and half knew that oil-based lubricants are not appropriate for condoms. The IDU population studied was young and requires additional interventions to encourage safer sexual behaviours.