To determine whether alcohol outlet density was correlated with heavy and frequent drinking and drinking-related problems, we compared ecological measures of outlet density with survey measures of drinking using a geographic information system and the Harvard School of Public Health College Alcohol Study (n=3,421, site n=8). We identified 966 outlets within 8 2-mile study areas. Densities/site ranged from 32 to 185. Density was correlated with heavy drinking (r=0.82, p=0.01), frequent drinking (r=0.73, p=0.04) and drinking-related problems (r=0.79, p=0.02). Women, underage students and students who picked up binge drinking in college were affected. Implications for prevention and research are discussed.