Twenty-four pigs were weaned at 21 days of age and given restricted feed allowances for the subsequent 8 days. Eight suckled pigs served as control and gained 320 g daily, of which approximately 40 g were lipid and 40 g protein. Pigs were slaughtered at 2-day intervals, physically dissected into non-carcass, carcass fatty tissue and carcass muscle plus bone, and these fractions were then analysed for water, protein and lipid. On average, weaned pigs made small positive body-weight gains. In comparison with suckled pigs, weaned pigs contained more water and less lipid but the same protein, and more non-carcass and less carcass fatty tissue but similar carcass muscle plus bone. Losses of lipid were offset by gains of water and associated with an increase in the percentage water content of carcass fatty tissue. At zero weight gain, pigs lost 43 g carcass fatty tissue, gained 37 g non-carcass, lost 56 g lipid and gained 53 g water, while carcass muscle plus bon e and protein gains were themselves not significantly different from zero. No change in carcass fatty tissue weight was associated with counterbalancing losses of lipid (18 g) and gains of water (15 g) and protein (3g). Lipid catabolism to support anabolism of essential body tissues commenced in the weaned pigs when weight gains fell below 193 g/day; this was about two-thirds of the gains achieved by the suckled control pigs. Plasma free fatty acid concentrations indicated that maximum lipid catabolism to occur on the 2nd day after weaning, and to reduce thereafter as body fat stores were progressively depleted.