1. Changes in body heat content in five normal adults, in 30 healthy children and in 24 children who had suffered burn injury 1–5 h previously, have been studied in cool (20°C) and warm (30°C) environments.
2. On moving from a cool to a warm environment, the heat content rose in both normal adults and healthy children, but the increase was significantly larger in the children.
3. Much larger changes occurred in the burned children in whom the heat content rose to a new plateau within about 8 h of the accident.
4. The changes after burn injury were unrelated to the bandaging of the burn and were little affected by the environmental temperature.