Introduction - In France, the prevention of infectious disease risk in prisons is governed by two documents issued jointly by the Ministries of Justice and Health: a 1996 circular and a methodological guide updated in 2004. The objective of this study is to estimate the risk of infection in French prisons by assessing the accessibility of the prevention measures recommended in these documents. Materials and Methods - A questionnaire was sent to the head of each medical unit in all French prisons in November 2009. Results - Sixty-six percent of institutions responded, covering 74% of the incarcerated population. A low level of accessibility to preventive measures was generally observed, particularly for bleach, opioid substitution therapy, condoms, post-exposure prophylaxis for HIV, and hair styling. Calculating a compliance score against both national and international recommendations helped to objectively highlight this gap between recommendations and actual practices. Conclusion - The French system for preventing infectious risks in prisons, already limited by regulations compared to that in the general community, is insufficiently implemented. The risk of infection is high, and a redefinition of healthcare and prevention policies in detention appears essential. It would also be desirable to allocate resources to expand and train healthcare teams, as well as other staff working in detention facilities. (R.A.)