PURPOSE: To analyse non-psychotropic drug prescription in a prison outpatient clinic in comparison with an urban medical outpatient service. METHODS: Comparative study during 3 weeks at Geneva: prison outpatient service and medical policlinic (MP) of the University Hospital. RESULTS: The most often prescribed non-psychotropic drugs at the Geneva prison were systemic analgesics (mostly non-steroidal anti-inflammatory drugs (NSAID) and paracetamol), dermatologicals, systemic anti-infectives and drugs for the gastrointestinal system. For most types of non-psychotropic drugs, frequency of prescription as well as the prescribing patterns were similar in the prison ambulatory service and the urban MP. Dermatologicals were prescribed more frequently at the prison than at the MP. Analgetics have been prescribed mainly for osteoarticulary reasons, especially low back pain at the MP, and for traumatism and headache at the prison. CONCLUSIONS: The higher frequency of dermatological prescriptions could be due to prison environmental factors. We do not have arguments for any overprescription of analgesics or other non-psychotropic drugs. The data did not show any prescription or co-prescription of several substances that violated clinical guidelines.