Coronary artery bypass grafting (CABG) is a commonly performed operation on Oklahoma Medicare beneficiaries. In 1994, the Centers for Medicare & Medicaid Services funded a project to evaluate process-oriented quality improvement activities for this surgery. Structured medical record review was performed on the charts of 2,312 Oklahoma Medicare patients who had a CABG surgery between July 1, 1995, and June 30, 1996, and on 926 patients who had their surgery from July 1 through December 31, 1998. Demographic, procedural and outcome variables were abstracted from each medical record. In addition to summarizing the clinical and demographic characteristics, we evaluated inter-hospital variations in both processes and outcomes of care. Significant variations in care were demonstrated for the 13 Oklahoma hospitals in which this operation was performed. The results of this project suggest that there are substantial opportunities to improve the quality of care for CABG in Oklahoma.