ABSTRACT: A school-based alcohol misuse prevention program had differential effects on students' susceptibility to peer pressure, depending on prior experience with alcohol. These effects paralleled those on alcohol use and misuse, indicating program effects on use and misuse were mediated by reductions in the rate of increase on susceptibility to peer pressure. Experimental group students with prior unsupervised use of alcohol showed a significantly greater reduction than their controls in the rate of increase in susceptibility to peer pressure, alcohol use, and alcohol misuse. This difference was not found among students without prior unsupervised use of alcohol.