Acid hydrolysis of Factor S of Staphylomycin has yielded the products: 3-hydroxypicolinic acid, L-threonine, D-α-aminobutyric acid, L-proline, N-methyl-L-phenylalanine, 4-oxo-L-pipecolic acid and L-phenylglycine. Further work has shown that the sequence of the (amino) acids is in the order given above and that a lactone linkage is present between phenylglycine and the hydroxy group of threonine.