The absorption of free glycine and L-tryptophan as well as amino acids released in the hydrolysis of glycil-L-leucine and glycil-L-tryptophan was studied in vitro with accumulating preparations of intestinal mucosa of 1-65-day old chicken. Two ways of absorption of free and peptide amino acids were found: sodium-dependent and sodium-independent. Intensity of each of them depended on the age of chicken and was dissimilar for the compounds. The sodium-independent way is more important for glycine than for free amino acid. Absorption of glycil-L-tryptophan as well as its amino acids is mainly performed by the sodium-dependent way.