The recruitment goal of Chicago Coronary Artery Risk Development in Young Adults (CARDIA) was 1,100 randomly selected young adults, in equal proportions for men and women, blacks and whites, two age groups, and two education groups. CARDIA is an ongoing multicenter study of the health and lifestyles of young adults designed to trace the development of risk factors for coronary heart disease over time. Participants completed a four-and-one-half hour exam and agreed to return two years later. In Chicago CARDIA, one of the four centers in the national collaborative study, random digit dialing of computer-generated telephone lists was the initial recruitment technique. Initial recruitment efforts resulted in too few low-socioeconomic status (SES) white participants and too few blacks. In response the sampling procedure was modified to focus on census tracts with a high density of blacks, more low-SES whites, and convenient public transportation. By being flexible, Chicago CARDIA improved recruitment in certain hard-to-fill cells and achieved the overall goals: 1,109 participants, 50% black and 50% white, near equal proportions by sex and age, and close to the recommended 40%/60% spread on education. The Chicago experience should benefit others conducting research in an urban setting.