An epidemiological survey was conducted to evaluate the prevalence of drug use among new entrants in Italian prisons. Overall, 1267 inmates were recruited by 9 prisons. Drug use before imprisonment was reported by 55.8% of the participants. Cocaine was the most commonly used drug (42%), followed by heroin (34%), marijuana/cannabis (33%), ecstasy (7%), hallucinogens (6%), amphetamines (5%); more than one drug was reported by 68% of abusers. Recent use (1 month before imprisonment) was admitted by up to 27% of inmates. Alcohol or tobacco use was reported by 38 and 77% of the inmates, respectively. Our findings indicate that a high proportion of inmates has ever used drugs; adequate intervention is needed to reduce the risk of addictive behaviour in this population group.