1. Food which provided from 2960 to 7880 kcal in excess of requirements was eaten by sixteen subjects, ten hospital patients and six students, in each instance for a period of 4 days.
2. The proportion of the nutrients lost in the faeces was not increased during overfeeding.
3. The metabolic rates were in no instance increased by an amount equivalent to more than 15% of the excess calories. The increase could be attributed to the specific dynamic action of the extra dietary protein.
4. The gains in weight ranged from 370 to 5460 g/4 days and the calorie equivalent of the weight gained varied from 1·1 to 10·0 kcal/g. These variations can be attributed to variations in the amount of water retained.
5. Analysis of their respiratory exchanges suggests that most subjects stored from 400 to 1500 g of carbohydrate in the tissues, possibly in the form of muscle glycogen.