This study uses Medicare enrollment and physician claims data to examine the effect of surgeon supply on the demand for surgeons' services. The specialties studied were ophthalmology, general surgery, orthopedic surgery, and urology. The study found that higher surgeon supply increases the demand for initial contacts with surgeons (first-occurrences demand) but does not affect the demand for services among surgeons' patients (intensity-of-care demand). These findings suggest that a high supply of surgeons improves access or is associated with stronger preferences for referrals to surgeons. The findings offer little support for the hypothesis that a substantial component of the additional utilization that occurs when surgeons are plentiful is due to increases in physician-induced demand.