With the aid of a computer-based anaesthetic record-keeping system, all cardiac arrests during anaesthesia at the Karolinska Hospital between July 1967 and December 1984 were retrieved. There were a total of 170 cardiac arrests and 250,543 anaesthetics in the data file, which gives an incidence of 6.8 cardiac arrests per 10,000 anaesthetics. Sixty patients died, constituting a mortality of 2.4 per 10,000 anaesthetics: 42 were considered as inevitable deaths (rupture of aortic or cerebral aneurysm, multitrauma, etc.); 13 cases of cardiac arrest were considered as non-anaesthetic, i.e. complications due to surgery and other procedures. Nine of these patients died. 115 cases of cardiac arrest were considered as caused by the anaesthetic and nine of these patients died. Thus mortality caused by anaesthesia was 0.3 per 10,000 anaesthetics. The most common cause of cardiac arrest due to anaesthesia was hypoxia because of ventilatory problems (27 patients), postsuccinylcholine asystole (23 patients) and post-induction hypotension (14 patients). The highest mortality was seen when spinal or epidural anaesthetics were given to patients with impaired physical status including hypovolaemia. The incidence of cardiac arrest has declined considerably during the period studied, and this coincides with an increasing number of qualified anaesthetists employed in the department during the same period.