Twenty-four Polish Landrace pigs (12 gilts and 12 barrows) fattened from 30 to 95 kg body weight were fed diets containing 18% rapeseed meal (RSM) and full-fat rape seeds (RS) in the following amounts: 0 (group RS-0), 10 (group RS-10) or 20% (group RS-20). The pigs were fed on an individual basis with rations having equal energy, protein and lysine contents. Nitrogen balance was determined at 40, 60 and 80 kg liveweight. Metabolizable energy and protein utilization were determined by the slaughter technique. The thyroid gland, liver and kidneys were weighed and plasma T₃ and T₄ levels assayed. Nitrogen retention was on average 12 and 17% lower (P<0.01) in groups RS-10 and RS-20 than in RS-0; the negative effect o rape seeds on nitrogen utilization intensified as fattening progressed. Metabolizable energy utilization in pigs receiving 20% RS was 2.5 and 3.4% worse (P<0.05) than in groups RS-10 and RS-0, respectively. As glucosinolates intake increased, the weight of the internal organs rose and T₃ and T₄ levels declined. These changes were not, however, proportional to the amount of glucosinolates intake. The combined use of RSM and RS in the diets of growing pigs had an unfavourable effect on protein and energy utilization.