This research analyzes the changes in individual physician surgical workload and accompanying changes in surgical rates in Manitoba, Canada between 1974 and 1978. Data covering essentially all operations on provincial residents age 25 years and older were analyzed using information from the health insurance data base. The most dramatic change was a 50% rise in outpatient surgery. An overall pattern of increased specialization seemed to be emerging; surgeons' surgical workloads were gradually growing while those of general practitioners were slowly declining. Changes in the frequency of several common surgical procedures were due much more to changes in workload of physicians remaining in the same hospital service area throughout the 1974-1978 period than to turnover (older physicians leaving practice and newer physicians coming in).