The purpose of the present study was to examine the effects of parental provision of alcohol and home alcohol accessibility on the trajectories of young adolescent alcohol use and intentions. Data were part of a longitudinal study of alcohol use among multi-ethnic urban young adolescents who were assigned randomly to the control group of a prevention trial. Data were collected from a cohort of youth, and their parents, who attended public schools in Chicago, Illinois (2002-2005). The sample comprised the 1388 students, and their parents, who had been assigned randomly to the control group and were present and completed surveys at baseline, in the beginning of 6th grade (age 12). The sample was primarily low-income, and African American and Hispanic. Students completed self-report questionnaires when in the 6th, 7th and 8th grades (age 12-14 years; response rates 91-96%). Parents of the 6th grade students also completed questionnaires (70% response rate). Student report, at age 12, of parental provision of alcohol and home alcohol availability, and parental report of providing alcohol to their child and the accessibility of alcohol in the home, were associated with significant increases in the trajectories of young adolescent alcohol use and intentions from ages 12-14 years. Student report of receiving alcohol from their parent or taking it from home during their last drinking occasion were the most robust predictors of increases in alcohol use and intentions over time. Results indicate that it is risky for parents to allow children to drink during early adolescence. When these findings are considered together with the risks associated with early onset of alcohol use, it is clear that parents can play an important role in prevention.