Phenylthiohydantoins of amino acids isolated from actinoidine (n-oxyphenylglycine, 3-chlor-4-oxyphenylglycine, actinoidinic amino acid) were prepared. Their spectral and chromatographic properties were studied. Splitting of the aglycone of actinoidine and the products of its incomplete acid hydrolysis (peptides Y-Phe and B-Y-Phe) was achieved with the Edman method. Partial structure of tripeptide B-Y-Phe (4NH2-group) was proposed. Tripeptide B-Y-Phe constitutes about 80% of the antibiotic aglycone part.