While the poor health status of prisoners has been highlighted in Western countries, the surveillance of their mortality has been neglected. We studied the mortality of 1305 prisoners released during 1997 from a French prison. Vital status after release was obtained for 86.4% of them. Compared with the general population, ex-prisoners non-natural mortality rates were significantly increased both in the 15-34 and 35-54 age categories (3.5-fold and 10.6-fold respectively) and the risk of death due to overdose was 124 and 274 times higher in the same categories respectively. Prevention and care should be reinforced in the pre-release period without waiting more epidemiological data.