OBJECTIVE To identify the incidence, causes, and characteristics of sudden death at age 1–20 years.

DESIGN A review of all deaths at age 1–20 years. Death certificates were obtained from the Office for National Statistics, and further information, where appropriate, from coroners, paediatricians, physicians, and pathologists.

SETTING The resident population of one English health region in 1985–1994.

RESULTS In a population of 806 500 children and adolescents aged 1–20 years there were 2523 deaths in 10 years. Medical causes accounted for 1017 deaths (40%); 1236 (49%) were unnatural, and 270 (11%) were sudden. These sudden deaths comprised 142 with a previous diagnosis, the commonest being epilepsy 49 (34%), cardiovascular disease 33 (23%), and asthma 30 (21%); 87 attributed to a cause discovered at necropsy, which was respiratory infection in 32 (37%), other infections in 17 (20%), and unsuspected cardiovascular abnormalities in 26 (30%); 41 remained unexplained.

CONCLUSIONS Half of all sudden deaths in children or adolescents were attributed to an already diagnosed condition. Abnormalities identified at necropsy accounted for one third of sudden deaths. Undiagnosed hypertrophic cardiomyopathy caused less than one death per million person years in the population aged 1–20 years. Unexplained sudden death, which may be caused by primary cardiac arrhythmia, is probably about 10 times more common.