While the extent to which HIV/AIDS has entered correctional facilities has been documented, less is known about the prevalence of HIV/AIDS high-risk behaviours among inmates: intravenous drug use, unprotected sex, tattooing, and piercing. The Correctional Service of Canada’s National Inmate Survey provided a unique opportunity to gather this information. Questionnaires were administered to a randomly selected sample of 4,500 male inmates. Results showed that HIV/AIDS high-risk behaviours are widespread in penitentiaries. Tattooing was the most prevalent behaviour (45%), followed by body piercing (17%), injection drug use (11%), and sexual intercourse (6%). The study showed that there were identifiable clusters of high-risk inmates. Younger inmates, parole violators, and those with a long criminal history including robbery/weapons offences had the highest risk for infection. A significant proportion of respondents felt that inmates were at greater risk of infection in prison than in the community.