Ferritin, an iron storage protein, has been purified from the last larval hemolymph of Protaetia brevitarsis (coleoptera) by KBr density gradient ultracentrifugation and resource Q(anion-exchange chromatography) using fast performance liquid chromatography (FPLC) system. The iron content of ferritin was determined by atomic emission spectroscopy and Ferene-S stain. Ferritin of P. brevitarsis is shown to have two different subunits presented on a SDS-PAGE in normal (N) and iron -injected (I) hemolymph. SDS-PAGE revealed that the ferritin consists of two major polypeptides of 27 and 28 kDa in normal hemolymph. Interestingly, however, 30 kDa subunit was substituted for 28 kDa when iron was injected into the hemolymph. Apporximate isoelectric points of 27 kDa, 28 kDa, and 30 kDa ferritin subunits were 6.7, 6.75, and 6.8, respectively. Ferritin of P. brevitarsis was detected by Ferene-S stain and confirmed by Western blotting using its polyclonal antibody. Other characteristics such as amino acid composition and N-terminal amino acid sequence were investigated. Amino acid composition of ferritin (N and I) was rich in alanine, glycine, glutamine or glutamic acid and serine, but poor in histidine, arginine, methionine and phenylalanine.