Physicians Health Study: A very large, long-term, randomized study initiated in 1982 to look at the effects of aspirin and beta-carotene on cancer and cardiovascular disease. Its finding that daily low-dose aspirin decreased the risk of a first myocardial infarction by 44% helped focus attention on the role of aspirin in primary prevention of heart attacks. The study also showed no benefit or harm from beta-carotene, a finding that allowed investigators to turn to other, more promising agents. Now in phase II, the Physicians' Health Study is testing the balance of benefits and risks of three other widely used, but as-yet unproven, supplements --vitamin E, vitamin C, and a multivitamin -- for the primary prevention of cardiovascular disease, cancer, and age-related eye disease. The participants, male physicians, are also tracked for other health issues. The Nurses Health Study is a comparable large long-term study of women's health issues. See: Nurses Health Study.