This study evaluated nearly 1500 hospitals to determine the relationship between their mortality rates and surgical volume for 12 selected procedures. Results include detailed tables of data and illustrative graphs for each procedure, suggesting a number of clear trends. Mortality associated with open-heart surgery, vascular surgery, transurethral resection of the prostate, and coronary bypass decreased with increasing volume at a given hospital. For other procedures, the mortality curve flattened at lower volumes, and some showed no relationship between volume and mortality. Although the authors recommend caution in interpretation and provide explanations for findings, they conclude that regionalization should warrant consideration for certain procedures.