1. The fatty acid composition of the depot fats of thirty-six preruminant lambs was determined. Four lambs were slaughtered at 3 d of age, two lambs were fed on a low-fat diet for 28 d, and thirty lambs in groups of three were given ten different dietary fats in artifcial milk diets for 28 d.2. The fatty acid patterns of the carcass fats were closely related to those of the dietary fats, and within-treatment variations were extremely low. Significant differences in fatty acid composition were observed between the skin, carcass, perinephric and subcutaneous lipids, irrespective of the diet given.3. The carcass lipids of lambs given the low-fat diet were similar in their fatty acid composition to those of lambs aged 3 d, though the former lambs lost fat from the carcass during the experimental period.