OBJECTIVES--To determine the pattern of drowning and near drowning of children in Britain and identify means of prevention. DESIGN--Study of drowned and nearly drowned children under 15 years old. SETTING--United Kingdom, 1988 and 1989. SUBJECTS--Children under 15 years either drowning or admitted to hospital after a submersion incident. MAIN OUTCOME MEASURES--Number of nearly drowned children, obtained from consultant paediatricians returning monthly notification cards through the British Paediatric Surveillance Unit. Number of drowned children notified by the Office of Population Censuses and Surveys and other national epidemiological offices; information from coroners. RESULTS--306 children had confirmed submersion incidents: 149 died and 157 survived after near drowning. The annual incidence in England and Wales was 1.5/100,000, and mortality 0.7/100,000. Mortality was lowest in public pools 6% (2/32) and highest in rivers, canals, and lakes (78%, 56/73). Most of the children (263, 83%) were unsupervised at the time of the accident. 208 (68%) children were under 5 years old. CONCLUSIONS--Drowning and near drowning of children are problems in the British Isles. Appropriate supervision and safety barriers seem important for preventing such accidents. Improving information on dangers of drowning given to parents through the child surveillance programmes, encouraging fencing or draining of garden ponds and domestic swimming pools, and increasing supervision of swimming in lakes, rivers, and beaches should reduce the number of accidents.