A study of childhood survival rates, after loss of consciousness in fresh water, has been undertaken. Age-specific, sex-specific and site-specific survival rates for childhood fresh water immersion accidents are reported for the first time. The overall survival rate, after loss of consciousness in the water was 0.49; swimming pool and domestic bath tub serious immersion accidents have a survival rate of 0.60 compared with a rate of 0.05 for similar immersion accidents in creeks and rivers. Young male schoolboys have the lowest potential survival (0.20 or less) of any group. Survival rates were significantly higher during the winter (0.86) than during the warmer months (survival rate of 0.49). This gives a quantitative expression to the protection from cerebral anoxia afforded by body chilling which is not extreme. Survival rates have increased significantly over the 5 year period 1971--1975; it is considered that this is due to public education campaigns of the potential danger of water to children. The use of survival rates to measure factors which modify the pathophysiology of human drowning and near-drowning is discussed.