ABSTRACT Objective: To assess the prevalence of drug abuse before prison admission and to identify associated sociodemographic and family history risk factors, according to gender, in prisons of Peru. Materials and methods: A secondary analysis was carried out with data from the First National Prisoner Census 2016, using a questionnaire of 173 items that was applied to the whole prison population of Peru. The types of drugs used before admission were analyzed according to characteristics of the penitentiary population, and generalized linear models were used to calculate prevalence ratios with 95% confidence intervals to identify possible factors associated with drug use. Results: Out of a population of 76,180 prisoners, 71,184 (93.4%) answered the survey (men 67,071, 94.2%). The overall prevalence of drug consumption before admission was 24.4% (25.3% in men and 9.1% in women), the highe...