BACKGROUND AND HYPOTHESIS: Although it is recognized that women have been underrepresented in clinical trials of cardiovascular disease, the reasons for their limited enrollment have not been elucidated. METHODS: A prospective tracking system was established in the Asymptomatic Cardiac Ischemia Pilot study (ACIP) to monitor recruitment and identify protocol issues that interfered with the recruitment of women. Patients with stress test evidence for ischemia during the course of routine clinical care were screened for asymptomatic ischemia with an ambulatory electrocardiogram (ECG). RESULTS: Those with at least one episode of asymptomatic ischemia and angiographic evidence of coronary artery disease suited for revascularization could be randomized. Women comprised only 17% of the 1,820 patients screened for asymptomatic ischemia, and only 14% of the 558 patients randomized. The limited number of women screened for ischemia was largely due to the limited number of women (25% of all patients) found to have test evidence for ischemia or coronary artery disease suited for revascularization during the course of routine clinical care. Once patients were identified as having ischemia on stress test and ambulatory ECG, the major difference in eligibility was the difference in disqualifying angiograms, occurring 21/2 times as frequently in women as in men (p < 0.001). CONCLUSION: The percentage of women recruited was lower than the prevalence of ischemic heart disease in the general population because at participating centers (1) women were found to have ischemia less often than men during the course of routine clinical care, and (2) screening tests for ischemia were less predictive of protocol-defined coronary disease in women than in men.