This study examined the relationship between coronary artery calcification and sleep duration in a sample of 495 participants (black and white men and women) aged 35-47 years who were followed for 5 years. Coronary artery calcification, measured by computed tomography, was absent in all participants at baseline, and the incidence of new calcification during the follow-up was considered the primary endpoint. The five-year incidence of calcification was 12.3%, and longer sleep duration was significantly associated with a reduced incidence of calcification (odds ratio=0.67/hour, 95% CI: 0.49-0.91, p=0.01). Adjustment for potential confounders did not alter this relationship. None of the other alternate sleep metrics were associated with incident calcification.