The Think First program was implemented in five NSW correctional centres between 2003 and 2007. This study is a longitudinal evaluation of Think First using the pre- and post-test scores of four questionnaire measures (the Social Problem Solving Inventory ' Revised; Barratt Impulsivity Scale, version 11; Locus of Control Behaviour; and the Crime PICS, version II), in a sample of 135 male participants. Significant change in a pro-social direction was found on the Locus of Control Behaviour, all of the Barratt Impulsivity Scale and Crime PICS II subscales and two of the Social Problem Solving Inventory - Revised subscales. Completion of Think First improved impulsivity levels, criminal thinking styles and some aspects of social problem solving ability. There appeared to be particularly positive effects on Aboriginal and Torres Strait Islander Locus of Control scores post-program.