To study associations between payer and provision of services for patients hospitalized for coronary atherosclerosis, the authors analyzed abstracts of 24,424 discharges from California acute care hospitals during 1989. Services examined included receipt of coronary artery bypass surgery, percutaneous transluminal coronary angioplasty (PTCA), long length of stay (LOS) without revascularization, and overall LOS. Regression techniques controlled demographic factors and comorbidities. The privately insured were 96% more likely to undergo revascularization (either bypass or PTCA) than Medicaid discharges and 117% more likely than the uninsured. Odds of revascularization for Medicare and health maintenance organization discharges resembled those for the privately insured. Analyzed separately, PTCA was far more likely among the privately insured than Medicaid beneficiaries and the uninsured. In addition, the adjusted odds for PTCA were 52% greater for the privately insured than for health maintenance organization discharges. The greatest likelihood of long LOS without revascularization and the greatest overall LOS was observed for Medicaid discharges. Strong associations, consistent with financial incentives to provide care, exist between payer and provision of services. Future studies need to address whether variations in process result from differences in thresholds for procedure performance, differences in admission practices, or both.