Protein and energy deposition in the body were measured in 20 pigs from 25 to 70 kg body weight, which were fed isoprotein and isoenergetic diets adequate (A) in ileal digestible amino acid content, deficient in lysine by 20% (D) or 40% (VD), or containing lysine and methionine in 20% excess (E). Protein deposition in VD and D pigs was respectively 26 and 9% lower, whereas in the E pigs it was similar to that in A pigs. Utilization of digestible lysine was inversely (r = -0.52) related to the amount of protein deposited in the body. Dietary supplementation with amino acids had no effect on utilization of metabolizable energy (on average 33%). However, heat production related to maintenance and protein deposition was reduced by 0.38 kJ/kg^0.75 (P = 0.07) per kJ energy additionally retained as protein.