The 4,390 participants came from an original 7th grade cohort from 30 schools. High-risk drinking included binge drinking, using of alcohol with marijuana, driving a car after drinking, becoming intoxicated, and other behaviors. Alcohol-related problems included missing school or work, feeling sorry, feeling really sick, getting into a fight, passing out, and other behaviors. Results revealed that by grade 12, nearly 70 percent of these adolescents had exhibited some form of alcohol misuse within the past year. Two-thirds had engaged in high-risk drinking and more than 50 percent had experienced one or more alcohol-related problems. More stringent estimates that required either a variety or persistence of risky drinking, alcohol-related problems, or both, revealed that between 40 percent and 54 percent of this population were alcohol misusers. However, focusing solely on high alcohol consumption failed to identify as many as half of these at-risk misusers. Findings also indicated that males and females both exhibited high rates of alcohol misuse, as did most racial and ethnic groups. However, black and Asian youth were less likely to misuse alcohol than were whites and Hispanics. Findings underscored the need for including different forms of alcohol misuse in prevention programs, for improving understanding of its causes, and for providing upper and lower estimates of alcohol misuse in future research. Tables, figure, and 45 references (Author abstract modified)