Cardiac arrests due solely to anesthesia were studied in a large university hospital over a 15-year period. There were 27 cardiac arrests among 163,240 anesthetics given, for a 15-year incidence of 1.7 per 10,000 anesthetics. Fourteen of these patients (0.9 per 10,000) subsequently died. Detailed examination of the data from these 27 patients revealed that the pediatric age group had a threefold higher risk than adults, and that the risk for emergency patients was six times that for elective patients. Failure to provide adequate ventilation caused almost half of the anesthetic cardiac arrests, and one third resulted from absolute overdose of an inhalation agent. Hemodynamic instability in very ill patients was an association in 22%. Specific errors in anesthetic management could be identified in 75%. Progressive bradycardia preceding the arrest was observed in all but one case.