The mortality associated with 338 934 procedures carried out in 1975 in 100 Finnish hospitals is reported. There were 626 deaths (1/541 or 0.18%). Mortality during the procedure was 1/5059 (0.02%). Twelve patients died primarily of anaesthesia during the procedures and 55 patients later (total anaesthetic mortality 1/5059, 0.02%). The frequency of cardiac arrest was 1/3808 (0.03%). Most of the 67 anaesthetic deaths were caused by inadequacy of management of fluid balance (17 patients) or respiratory insufficiency (15 patients). There were 12 deaths from cardiac complications, five each from technical errors and inadequate supervision after operation. The primary disease was responsible for approximately 72% of the reported deaths.