The analyses reported of protein, fat and sugar indicate a high fat and a low carbohydrate diet for the suckling rat. Fats comprise approximately 55 per cent of the solids in rat's milk, approximately 30 per cent are proteins, and approximately 15 per cent are carbohydrate. Calculating the proportion of calories upon the basis that fat yields 9.3, protein about 4, and disaccharides 3.95 calories per gram, 74 per cent of the calories in the diet of the suckling rat are furnished by fat, 18 per cent by protein, and only 8 per cent by carbohydrate. In spite of the great proportion of fat in the diet of the suckling rat, this diet is not an extremely ketogenic one. The ketogenic-antiketogenic ratio, calculated as suggested by Shaffer ('21 a, '21 b, '22), is 1.35:1.