Accurate up-to-date data on the extent of drug use and the prevalence of blood-borne viruses among the prisoner population are a necessary pre-requisite for health and social service planning and policy development. The most recent national study assessing the prevalence of blood-borne viruses, along with self-reported drug use within Irish prisons (Allwright et al., 1999),was carried out over a decade ago. This study was commissioned by the National Advisory Committee on Drugs (NACD)* in 2010 with the following objectives: to describe the nature, extent and pattern of consumption for different drugs among the prisoner population; to describe methods of drug use, including intravenous drug use, among the prisoner population; to estimate the prevalence of blood-borne viruses among the prisoner population and to identify associated risk behaviours; and to measure the uptake of individual drug treatment and harm reduction interventions (including hepatitis B vaccination)in prison.