Underage drinking is a major problem at American colleges, but little is known about the extent of alcohol use in different student groups, in different colleges, and in states with different control policies. We used data from the 2001 and 3 previous Harvard School of Public Health College Alcohol Studies that compared responses of underage students with those of their 21-23-year-old peers. Underage students drank alcohol less frequently but were more likely to drink to excess when they drank. College educational efforts and deterrent policies were limited in their outreach, and half of underage students obtained alcohol very easily. Underage students in states with extensive laws restricting underage and high-volume drinking were less likely to drink and to binge drink. A majority of underage students supported increasing efforts to control underage drinking. The results suggest that additional policy efforts to control underage drinking may be effective and feasible.