Twenty three sporadic cases of Reye's syndrome diagnosed according to widely accepted criteria were seen between 1979 and 1982. The patients were younger than those reported from North America (median age 9 months), girls were twice as common as boys, and the syndrome presented twice as frequently in the summer 6 months. The annual incidence was 1.4 cases/100 000 among children aged less than 4 years. The prodrome consisted of upper respiratory symptoms in 61% of the children and even less specific features in more than 25%; two patients had varicella. Six of the 23 patients presented after a prodrome of less than 24 hours with 'acute collapse', simulating 'near miss' cot death associated with profound hypoglycaemia, and in four of these there was an unfavourable outcome. Intensive care methods including judicious fluid restriction coupled with 'prophylactic' hyperventilation (87%), direct monitoring of intracranial pressure (70%), and barbiturate coma (52%) achieved neurologically intact survival in 74% of patients. Failure to recognise the syndrome early enough or to manage it appropriately resulted in four deaths. To help reduce overall mortality in the United Kingdom paediatricians have a duty to acquaint family doctors and emergency department staff of the earliest clinical features of Reye's syndrome and of the need for immediate hospital referral.