The School Health and Alcohol Harm Reduction Project (SHAHRP) aimed to reduce alcohol-related harm by enhancing students' abilities to identify and deal with high risk drinking situations and issues. The SHAHRP study involved a quasi-experimental research design, incorporating intervention and control groups and measuring change over a 32 month period. The study occurred in metropolitan, government secondary schools (13-17 year olds) in Perth, Western Australia. The fourteen intervention and control schools involved in the SHAHRP study represent approximately 23% of government secondary schools in the Perth metropolitan area. The sample was selected using cluster sampling, with stratification by socio-economic area and involved over 2300 intervention and control students from junior secondary schools. The retention rate of the study was seventy six percent (75.9%) over 32 months. The intervention incorporated evidence-based approaches to enhance potential for behaviour change in the target population. The intervention was a classroom based program, with an explicit harm minimisation goal and was conducted in two phases over a two year period. The results were analysed by baseline context of alcohol use to assess the impact of the program on students with varying experience with alcohol. Knowledge and attitudes were simultaneously modified after the first phase of the intervention in all baseline context of use groups. The program had little behavioural impact on baseline supervised drinkers, however, baseline non drinkers and unsupervised drinkers were less likely to consume alcohol in a risky manner, compared to their corresponding control groups. In line with program goals, early unsupervised drinkers from the intervention group were also significantly less likely to experience harm associated with their own use of alcohol compared to the corresponding control group. Unsupervised drinkers experienced 18.4% less alcohol related harm after participating in both phases of the program and this difference was maintained (19.4% difference) 17 months after the completion of the program. This study indicates that a school drug education program needs to be offered in several phases, that program components may need to be included to cater for the differing baseline context of use groups, and that early unsupervised drinkers experience less alcohol related harm after participating in a harm reduction program.