The clinical features, plasma salicylate concentrations, acid-base abnormalities and other biochemical findings are presented for 97 patients who either died from acute salicylate overdosage or survived maximum recorded plasma salicylate concentrations of 700 mg/l or greater. These patients comprised 4 per cent of 2204 cases of salicylate poisoning admitted during the period 1975 to 1985 inclusive. Seven patients died (overall mortality 0.3 per cent); they were significantly older than the survivors, the mortality being as high as 33 per cent in patients over the age of 70 years. Delayed presentation, coma, hyperpyrexia, pulmonary oedema and acidaemia were more common in the fatal cases. Failure to hyperventilate appropriately may contribute to the development of acidaemia. The prognosis of acute salicylate poisoning cannot be determined from the plasma concentration of the drug alone. Clinical features, particularly impaired consciousness, and the arterial hydrogen ion concentration must be taken into consideration. Haemodialysis is the treatment of choice for severe salicylate intoxication and should be used more liberally than it is at present.