The standardized ileal digestibility/true ileal digestibility (SID/TID) of protein and amino acids (AA) in low- and high-tannin pea seeds and soyabean products (soyabean meal, raw soyabean, extruded soyabean) containing different levels of trypsin inhibitor activity was determined and compared in growing cannulated pigs, in adult rats and using in vitro method. Endogenous losses of protein and AA at the ileal level were estimated in rats after feeding protein-free diet and were found to be similar to tabulated values for pigs. Protein and AA SID was significantly higher in pigs fed with low- than with high-tannin pea. In rats, AA TID was also higher in animals fed low-tannin pea, however, values were significantly different only for few AA. The in vitro AA SID measured in six pea cultivars decreased linearly with increasing tannin contents. Addition of raw soyabeans to a diet significantly decreased protein and AA SID/TID in both animal species, as compared to soyabean meal diet. The in vitro protein and AA SID was not affected by trypsin inhibitor activity. In conclusion, to rank feedstuffs according to their AA digestibility for pigs using alternative methods, the in vitro method is suitable for peas containing different levels of tannins, while rats are sensitive enough to trypsin inhibitor activity to differentiate soyabean feedstuffs.