The results of research on the apparent ileal and total digestibility of nitrogen and amino acids in mink and polar foxes are presented. The research reveals lower values of apparent nitrogen and amino acid digestibility coefficients in the small intestine than in the whole alimentary tract of these animals fed on diets containing different sources of animal protein. Fresh fish proteins showed higher ileal and total digestibility of nitrogen and amino acids than fish meal proteins. The increase or sole content of fish meals in the diets caused more rapid digesta passage, a rise in the amount of voided faeces and lower apparent ileal and total digestibility of nitrogen and amino acids. After diets containing whole fish and beef, the amino acids with the highest digestibility were methionine and lysine. After the diets containing fish meal, meat meal, meat-and-bone meal, and poultry by-product meal, arginine was the amino acid that was the quickest to be absorbed from the small intestine in mink and polar foxes. The amino acids of the lowest availability in the small intestine, as well as in the whole alimentary tract of these species appeared to be threonine and cystine. The lowest apparent digestibility of these amino acids probably resulted from their high content in endogenous nitrogen released in the digestive tract of mink and polar foxes.