A protein nerve growth factor has been isolated in the pure form from the muscles of the lake frogRana ridibunda. The individuality of the substance obtained has been shown, its molecular mass (106.0–110.0 kDa) and pI value (9.2–9.4) have been determined, and lysine and valine have been found as the N- and C-terminal amino acid residues of its polypeptide chain. In view of the detection of the presence of sugars (about 1%), the substance has been identified as a glycoprotein. Its absorption spectra in the UV region has been obtained and the amino acid composition of the isolated protein has been determined. Information on the amino acid composition of various proteins with nerve growth activity has been subjected to comparative analysis with the aid of computer programs, and on this base their phylogenetic “tree” has been constructed.