The Raloxifene Use for The Heart (RUTH) trial is a randomized, placebo-controlled, double-blind trial designed to determine whether raloxifene 60 mg/day compared with placebo lowers the risk of coronary events (coronary death, nonfatal myocardial infarction [MI], or hospitalized acute coronary syndromes other than MI) and reduces the risk of invasive breast cancer in women at risk for a major coronary event. Raloxifene is a selective estrogen receptor modulator that improves cardiovascular risk factors, reduces the risk of vertebral fracture, and is associated with a reduced incidence of invasive breast cancer in postmenopausal women with osteoporosis. Between June 1998 and August 2000, 10,101 women were enrolled at 187 sites in 26 countries. Approximately half of the women had documented coronary heart disease (CHD) (n = 5,031); the remainder had multiple CHD risk factors that increased their risk for a CHD event (n = 5,070). The mean age of participants was 68 years (39% were >70 years old), and did not differ between those with documented CHD and those at increased CHD risk. Most women were Caucasian (84%); 60% had a body mass index >/=27 kg/m(2), 46% had diabetes mellitus, 78% had systemic hypertension, and 14% had low-density lipoprotein cholesterol >160 mg/dl. Compared with women at increased CHD risk, women with documented CHD had higher cardiovascular risk scores, a higher prevalence of abnormal electrocardiograms, greater use of cardiovascular medications, were more likely to have had cardiac rehabilitation, and were more likely to have previously used estrogen or oral contraceptives, but had a slightly lower prevalence of CHD risk factors such as smoking, obesity, diabetes mellitus, and systemic hypertension, and had lower serum levels of total and low-density lipoprotein cholesterol. The RUTH cohort is the largest group of postmenopausal women at increased risk of CHD events ever assembled in a clinical trial, and is the first trial designed to determine the effect of a selective estrogen receptor modulator on the risk of CHD events.