The effect of white cv. Bardo lupin seeds on the fattening performance of 35 barrows weighing 24 to 96 kg was determined. In the first period of fattening (growing up to 65 kg) the proportion of lupin seeds in the diets was 0, 8 and 14%, in the second period (finishing) 0, 14 and 20%. The amounts of lupin used replaced 0, 30 and 50% of soyabean meal in the growing, and 0, 75 and 100% in the finishing diets. The effectiveness of an enzymatic preparation containing β-glucanase and xylanase supplementing diets with varying proportions of soyabean and lupin and barley (52-65%) was also studied. The digestibility of dietary nutrients, nitrogen balance, daily weight gain and feed utilization were estimiated. The addition of white lupin seeds, containing 0.067% DM alkaloids, instead of soyabean meal did not have an unfavourable effect on nutrient digestibilities or nitrogen retention. Daily weight gains and feed utilization in pigs fed mixtures with an 8% (growing) and then 14% (finishing) lupin were the same as in the control group receiving soyabean meal. The higher proportion of lupin in the diets, i.e. 14% in the growing and 20% in the finishing diet, significantly decreased the growth rate of the pigs and feed utilization. The addition of the β-glucanase and xylanase preparation (0.1% Porzyme 9100) increased only the digestibility of N-free extractives in the diets for young pigs (about 55 kg) and in both periods of fattening increased daily nitrogen retention.The daily gains were higher (3.6%) and the feed utilization was better (4%) in pigs fed diets supplemented with enzyme preparation, but differences were not significant.