The Minnesota Adolescent Community Cohort (MACC) Study is a population-based, longitudinal study that enrolled 3,636 youth from Minnesota and 605 youth from comparison states ages 12 to 16 years in 2000-2001. Participants have been surveyed by telephone semi-annually about their tobacco-related attitudes and behaviors. The goals of the study are to evaluate the effects of the Minnesota Youth Tobacco Prevention Initiative and its shutdown on youth smoking patterns, and to better define the patterns of development of tobacco use in adolescents. A multilevel sample was constructed representing individuals, local jurisdictions and the entire state, and data are collected to characterize each of these levels. This paper presents the details of the multilevel study design. We also provide baseline information about MACC participants including demographics and tobacco-related attitudes and behaviors. This paper describes variability in smoking prevalence and demographic characteristics for local units, and compares MACC participants to the state as a whole.