This article presents an analysis of over 140,000 selected surgical procedures performed in Massachusetts in 1980, giving the per capita rates of 14 common procedures and of four less frequently performed procedures. The analysis defines 172 geographic areas for the commonly performed procedures and 45 for the less frequently performed procedures. Per capita surgical rates among the defined areas are significantly different from both a statistical and a clinical point of view. Twofold and threefold variations occur frequently across geographic areas. In certain areas, some surgical services appear to be provided at rates substantially different from the statewide rate. We discuss the importance of these data for physicians as well as the implications for the distribution and quality of clinical care and for containment of medical care costs.