To determine if supplements of vitamin C, vitamin E, beta-carotene, and B-vitamins (a combination of folic acid, vitamins B6 and B12) reduce risk of major cardiovascular events in high risk women with a prior history of atherosclerotic cardiovascular disease. The trial is a companion to the Women's Health Study (WHS), a primary prevention trial of vitamin E and aspirin in a low risk population of women.

The Women's Antioxidant and Folic Acid Cardiovascular Study tested the effects of vitamin C (500 mg/day), vitamin E (600 IU every other day), and/or beta carotene (50 mg every other day) on the risk of major cardiovascular events (a combined outcome of myocardial infarction, stroke, coronary revascularization, or cardiovascular death) among 8171 female health professionals at increased risk. Participants were 40 years or older with a history of cardiovascular disease or 3 or more cardiovascular risk factors and were followed for an average duration of 9.4 years, from 1995-1996 to 2005. In 1998, 5442 of these participants were further randomized to the B-vitamin intervention (a daily combination pill containing folic acid [2.5 mg], vitamin B6 [50 mg], vitamin B12 [1 mg]) and were followed for 7.3 years, from April 1998 through July 2005.

Women, aged 40 and over, at high risk, with a history of cardiovascular disease or three or more coronary heart disease risk factors.