The effect on the performance of reduced amino acid intake were verified on 72 gilts for the growing-finishing period. The gilts were divided in 3 groups that were fed on 3 different diets that had the same level of digestible ideal protein but not the same level of crude protein; for the growing period for 20 to 55 kg the diets contained .66% of apparent ileal digestible lysine for crude protein content of 16.6, 15.0 and 13.0% respectively and for the finishing period from 55 to 100 kg the digestible lysine content was .55% for CP of 14.2, 12.8 and 11.0% respectively. The different CP treatments did not affect the performances, daily gain, feed intake, and gain:feed for the growing and overall growing-finishing periods. However during the finishing phase the gilts fed on 11.0% CP diet showed lower daily gain and poorer gain:feed. Even if the estimated carcass lean yield was not affected by the diets, the backfat thickness tended to be greater for the gilts fed low CP diets. The results show that as long as crystalline amino acids (lysine) are added to the diets the performance of pigs wont be significantly affected for diets that are at 13% CP for the growing period and 12.8% CP for the finishing period.