AIMS: To describe the self-reported routes of administration of illicit drugs among subjects entering a remand prison and the different drugs used by this population. METHODS: A cross-sectional study, with a sample of 770 subjects, was conducted in Geneva (Switzerland). Participants were assessed with the semi-structured interview from the Council of Europe Pompidou Group multi-city study. RESULTS: 428 (55.6%) subjects admitted to having used illicit drugs during the 3 months prior to entry. Amongst these illicit drug users, 54.7% took several drugs. Injectable drugs (heroin, cocaine or illicit benzodiazepines) were taken by 75.7% of drug users but the majority (84.1%) declared that they had not injected drugs during the 3 months prior to entering prison. 68 subjects (8.8% of the total sample) declared that they had injected drugs during the 3 months prior to entering prison, either alone or in association with other methods. CONCLUSION: By extrapolation it is possible to suggest that about 200 intravenous drug users entered the remand prison in Geneva in 1 year. This confirms the need for prison health services to implement a policy of treatment, prevention and education adapted to patterns of drug use in the local context.