Thirty six Landrace pigs from 60 to 110 kg liveweight were given diets of similar available lysine and metabolizable energy contents. The feed mixtures contained an average of 16% soya bean meal (SBM) or 21% rapeseed meal (RSM) of a double-low variety (8.7 moles glucosinolates per g fat-free dry matter). Energy retention in the body was measured by the comparative slaughter technique. The weight of the internal organs and thyroid gland and T₃ and T₄ hormone concentrations in blood samples taken at slaughter were also determined. The weight of the thyroid and liver were 55% (P≤0.001) and 16% (P≤0.001) higher, respectively, in the animals fed RSM. The RSM diet caused no significant difference in the chemical composition of the body gain, blood T₃ and T₄ levels as in the weight of the kidneys. The maintenance requirement and energy cost of protein deposition in the body of pigs did not differ between the groups (511 kJ/kg^0.75/d and 68 kJ/g, respectively).