Objective: To identify precursors of adolescent alcohol initiation and binge drinking. Design: Prospective cohort study. Setting: Self-report questionnaires. Participants: A total of 5511 Growing Up Today Study participants aged 11 to 18 years in 1998. Main Exposures: Individual, family, and social factors. Main Outcome Measures: First whole drink of alcohol and binge drinking. Results: Between 1998 and 1999, 611 girls (19%) and 384 boys (17%) initiated alcohol use. Older age, later maturational stage, smoking, adults drinking in the home, underage sibling drinking, peer drinking, possession of or willingness to use alcohol promotional items, and positive attitudes toward alcohol were associated with an increased likelihood of alcohol initiation. Girls who ate family dinner at home every day were less likely to initiate alcohol use than girls who ate family dinner only on some days or never (odds ratio, 0.66; 95% confidence interval, 0.50-0.87). Girls with higher social self-esteem and boys with higher athletic self-esteem were more likely to initiate alcohol use than those with lower selfesteem. Among teens who initiated alcohol use, 149 girls (24%) and 112 boys (29%) further engaged in binge drinking. Among girls, positive attitudes toward alcohol, underage sibling drinking, and possession of or willingness to use alcohol promotional items were associated with binge drinking; among boys, positive attitudes toward alcohol and older age were associated with binge drinking. Conclusions: Eating family dinner at home every day may delay alcohol uptake among some adolescents. Alcohol promotional items appear to encourage underage alcohol initiation and binge drinking; this may warrant marketing restrictions on the alcohol industry.