Project Northland, an ongoing community trial aimed at reducing alcohol use and alcohol-related problems among adolescents, is nearing completion. The project combines individual-based strategies to encourage adolescents not to use alcohol with community-based strategies to both reduce alcohol availability and modify community attitudes concerning youth drinking. Project Northland has developed prevention programs and followed the same group of adolescents from sixth grade to high school graduation. This article discusses the rationale for this type of program, elements of the adolescents' social environment targeted for change, the unique challenges of working with high school students compared with younger adolescents, and areas for future research.