Women, ethnic minorities, and uninsured persons receive fewer cardiac procedures than affluent white male patients do, but rates of use are crude indicators of quality. The important question is, Do women, minorities, and the uninsured fail to receive cardiac procedures when they need them? To measure receipt of necessary coronary artery bypass graft (CABG) surgery and percutaneous transluminal coronary angioplasty (PTCA) overall; by patient sex, ethnicity, and payer status; and by availability of on-site revascularization. Retrospective, randomized medical record review. 13 of the 24 hospitals in New York City that provide coronary angiography. 631 patients who had coronary angiography in 1992 and met the RAND expert panel criteria for necessary revascularization. The percentage of patients who had CABG surgery or PTCA was measured, as were variations in use rates by sex, ethnic group, insurance status, and availability of on-site revascularization. Clinical and laboratory data were retrieved from medical records to identify patients who met the panel criteria for necessary revascularization. Receipt of revascularization was determined from state reports, medical records, and information provided by cardiologists. Overall, 74% (95% CI, 71% to 77%) of patients who met the panel criteria for necessary revascularization had CABG surgery or PTCA (underuse rate, 26%). No differences were found in use rates by patient sex, ethnic group, or payer status, but hospitals that provided on-site revascularization had higher use rates (76% [CI, 74% to 79%]) than hospitals that did not provide it (59% [CI, 56% to 65%]) (P < 0.01). In hospitals that did not provide on-site revascularization, uninsured patients were less likely to have revascularization recommended to them (52% [CI, 32% to 78%]); rates of recommendation for patients with private insurance, Medicare, and Medicaid were 82%, 91%, and 75%, respectively (P = 0.026). Although revascularization procedures are substantially underused, no variations in rate of use by sex, ethnic group, or payer status were seen among patients treated in hospitals that provide CABG surgery and PTCA. However, underuse was significantly greater in hospitals that do not provide these procedures, particularly among uninsured persons.