Physician specialty has been consistently associated with different malpractice claim rates, with neurosurgery, orthopedics, and obstetrics and gynecology having the highest rates. Whether these differences reflect physician performance or other aspects of patient care that are unique for each specialty is unclear. A retrospective cohort study was performed including 12,829 physicians involved in 8,221 closed cases from 1977 to 1991. For each case an assessment was made whether the plaintiff received an award and whether the physician care of the patient was indefensible. An award was made to the plaintiff in 42% of cases. Physician care was considered indefensible in 23% of the cases. The specialties with the highest award rates were anesthesiology (58.3%), obstetrics and gynecology (47.5%), and radiology (43.0%). Neurosurgery had the lowest rate of award (30.2%). The specialties with the highest indefensibility rates were radiology (36%), obstetrics and gynecology (27%), and anesthesiology (27%). Neurosurgery had the lowest indefensibility rate (10%). These results were unchanged after controlling for physician age, degree, site of training, certification status, and severity of patient injury. In conclusion, differences in award rate and indefensibility are present, but not large enough to explain the large variation in specialty claim rates. This suggests that the variation in malpractice rates results from factors other than a meaningful difference in physician performance.