The digestibility experiment was carried out on twelve cannulated pigs between 14 and 27 kg body weight. The animals were fitted with a PVTC cannula and fed with two starter diets, A and B, differing in metabolizable energy content (13.5 and 14.5 MJ ME/kg, respectively), with no supplemented amino acids (AA), in order to measure digestibility coefficients of protein-bound AA. The diets were formulated to contain 0.6 g ileal digestible lysine/MJ ME and were calculated on the basis of AA analysis of ingredients and their tabular values of apparent ileal AA digestibilities. For both diets, differences between the calculated and determined digestibilities of the limiting essential AA were found. The determined digestibilities tended to be lower than the calculated ones. Of the essential AA, the differences were greatest for threonine (6.8 and 9.5% of calculated values for diet A and B, respectively) and lysine (4.3 and 8.3% for diet A and B, respectively); the differences for methionine and tryptophan ranged from 4.0 to 6.2%. In conclusion, the present study shows that the digestible AA supply in a diet can be predicted from total AA content determined in the individual ingredients and from average literaturę values recommended for their AA digestibility, however, it is necessary to accept an 8–10% error for calculated values.