1. The effects on body composition, measured by direct techniques, of a controlled 25% body-surfacearea thermal injury have been studied in two groups of forty male Wistar rats.
2. The extent of weight loss in the animals was directly related to their energy deficit resulting from a combination of injury, food intake and rate of wound healing.
3. Body fat proved the most labile source of tissue energy, decreasing to a minimum of approximately 30 g/kg body-weight.
4. Relationships between water and fat, and water and protein seen in control animals were not significantly different in the traumatized group.