L-Cysteinylglycine is present in wheat germ. The peptide was isolated as the S-carboxymethyl-2-14C derivative. The identity of S-carboxymethyl-L-cysteinylglycine was determined by amino acid analysis, N-terminal analysis, and mass spectroscopy. L-Cysteinylglycine appears to be widespread in nature as it is found also in E. coli, murine tissue, and human serum. It does not seem to be present in yeast.