Summary: Objectives:: The aim of the study was to obtain an overview on diagnostic and therapeutic activities concerning hepatitis A, B, C virus and HIV in Swiss prisons. Methods:: A standardized questionnaire was sent to 91 prisons in the German and Italian speaking parts in October 2004; 41 institutions (45%) answered the questionnaire. Results:: In almost all prisons serological examinations were not done routinely, but were provided when demanded by inmates or recommended by the medical service. Vaccination against hepatitis A or B infection and initiation of antiviral therapy was possible in most institutions. Conclusions:: Most of the prisons investigated offered diagnostic and antiviral treatment for hepatitis virus and HIV infections. A reported problem was the discontinuation of ongoing treatments or vaccination cycles after discharge. In some cases deficient funding was an obstacle