The vitellin of firefly, Pyrocoelia rufa, is composed of three polypeptides, designated Vn1 (175 kDa), Vn2 (160 kDa) and Vn3 (45 kDa) in SDS-polyacrylamide gel electrophoresis. Three subunits of vitellin were presented in the female adult hemolymph, ovary and egg extracts, but not observed in the male. This vitellin was purified from the eggs of P. rufa by the FPLC techniques, anion exchange chromatography and gel permeation chromatography. In nature, vitellin of P. rufa has molecular weight of 400 kDa. Western blot analysis using polyclonal antiserum against purified vitellin showed that the antiserum was reacted with the three polypeptides, Vnl, Vn2 and Vn3 from the female adult hemolymph, ovary and egg extracts. Amino acid residues at N-terminus of three subunits were sequenced. The N-terminal sequences of large subunits, Vnl and Vn2, were similar to each other, But, the N-terminal sequences of small subunits Vn3, did not have any signnificant homology with large subunits.