Despite the established benefits of antiplatelet agents in coronary artery disease (CAD), many appropriate patients are not receiving them. We investigated the prevalence of and factors associated with aspirin use and nonuse within a large referral population with CAD. The goal was to identify an approach to increase the use of antiplatelet agents by such patients. We surveyed a subset (n = 2,694) of a large CAD referral population (n = 16,174) to determine the use of aspirin and factors associated with its use or nonuse. The subset was made up of all of the CAD referral population who were considered nonusers of aspirin and a 5% sample of those considered aspirin users. We then extrapolated survey data to the overall population to estimate how many eligible patients were not taking antiplatelet agents. In all, 1,626 (63%) of the surviving patients responded to the survey. Of these, 948 (58%) reported taking aspirin, and 678 (42%) reported no aspirin use. The extrapolated rate of aspirin use in the overall population was 85%. Of 2,367 nonusers, 998 (42%, or 6% of the overall cohort) were eligible for antiplatelet agents but were not taking such therapy. Although the rate of aspirin use in this population was higher than previously reported, an estimated 6% of eligible patients were not receiving antiplatelet therapy.