The Quebec government considers program evaluations to be a necessity if public organizations are to monitor and improve their performances. However, relatively few evaluations are conducted in prisons, despite the important need for programs in such an environment. The numerous challenges that face researchers who attempt such evaluations may partially explain the reluctance to undertake them. This article traces and explains the process used by a team of researchers in evaluating an addiction program in a provincial prison. The article describes the challenges and problems faced by the team and the strategies that were implemented to overcome these challenges.