Amino acid composition, partial or complete sequence of 43 tryptic peptides of pelyhedral protein of nuclear polyhedrosis virus is investigated. These peptides include 327 amino acid residues. There are 28 peptides with unique sequences containing 240 amino acid residues. It conforms to polypeptide chain molecular weight ca. 28000 and coincides with earlier reported data on polyacrylamide gel electrophoresis.