In 1974 there was five-to eight-fold variation in the frequency with which tonsillectomy, colectomy, hysterectomy, cholecystectomy and appendectomy were performed in Ontario's 49 counties. All five procedures were resource sensitive; over 50 per cent of the variation in rates was explained by numbers of acute care treatment beds and physicians. Generally, counties with high or low rates for any one procedure had corresponding rates for the other four. The highest rates were found in less populous rural eastern Ontario counties, while university teaching centers ranked among the lowest for all five operations although they had the highest ratios of beds, general practitioners and surgeons. Linkages between university medical centers and community hospitals, widespread dissemination of surgical rate data, surgical audit and review of surgical indications and practices in university centers and community hospitals are proposed to aid in rationalizing surgical practices in Ontario.