A prospective survey of complications associated with anaesthesia was carried out in France from 1978 to 1982 in a representative sample of 198,103 anaesthetics performed in 460 public and private institutions chosen at random in the country as a whole. There were 268 major complications associated with anaesthesia occurring during or within 24 hours of anaesthesia (one per 739 anaesthetics), among which 67 were followed by death within 24 hours and 16 by coma persistent after the 24th hour. The incidence of death and coma was one per 2387 anaesthetics. The incidence of death and coma totally attributable to anaesthesia was one per 7924 anaesthetics. Fifty-eight per cent of complications occurred during anaesthesia while 42 per cent were observed during the recovery period. Mortality was lower following complications during anaesthesia than for those during the recovery period. Half of the deaths and cases of coma totally attributable to anaesthesia were due to postanaesthetic respiratory depression. The rate of complications appeared to be dependent upon several risk factors: the patient's age, the number of associated diseases, the preoperative status, whether the operation was an emergency and the duration of procedure.