Pregnant guinea pigs were fed one of three diets: a control low-fat diet or a high-fat diet containing maize oil or beef tallow. Offspring were reared on the same diets as their mothers. At 12 weeks of age some animals were killed; others had their food intake restricted for 2 weeks and were then killed. Body weight, weight of various adipose tissue depots and size and number of fat cells were measured. All adipose depots decreased in weight during food restriction and fat cell size was reduced. Perirenal adipose tissue lost the greatest amount of weight and the gonadal depot the least. Fat cell number in females was unaffected by food restriction, whereas in males the number of observable fat cells decreased in the perirenal depot. Previous diet influenced the amount of body weight lost during food restriction. Animals fed beef tallow lost less weight than those fed maize oil. Possible reasons are discussed.