To study red cell transfusion practice in 3216 coronary artery bypass graft (CABG) cases in 11 hospitals in 1988, abstracted patient records were stratified by diagnosis related group (DRG) (that is, DRG 106, coronary artery bypass without catheterization, or DRG 107, coronary artery bypass with catheterization) and International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) surgical procedure code. Means of units per transfused patient, age and length of stay, and in-hospital mortality rates were significantly greater for patients in DRG 106 than DRG 107. Gender was a significant factor for transfusion outcomes; female patients were more likely to undergo transfusion, and, when transfused, they received more units of red cells than male patients. For a given DRG/ICD-9-CM surgical procedure class, significant differences were found between hospitals in the percentage of patients transfused, but not in mean units of red cells per transfused patient. However, within individual hospitals, the proportion of patients transfused and the number of units per transfused patient did not vary significantly across DRG/ICD-9-CM procedure classes. These results suggest that circumstances operating within a hospital, still to be identified, had more influence on transfusion decisions than the nature of the surgical intervention.