The molting hormone β-ecdysone (20-hydroxyecdysone) has a great influence on the development of insect. Also, β-ecdysone induced synthesis of the HSP23 as one of the small heat shock proteins in vitro. However, α-ecdysone and 20-hydroxyecdysone-22-acetate didn`t effect the synthesis of the HSP23. In this study, the biosynthetic correlation between the β-ecdysone and the HSP23 according to development was investigated in Drosophila melanogaster Or-R wild type. We prepared the anti-β-ecdysone antiserum and anti-HSP23 antiserum. Due to the small size of β-ecdysone, this molecule can not be the immunogenic substance. This, the β-ecdysone were covalently coupled to bovine serum albumin (BSA) or rabbit serum albumin (RSA) and then used to immunization of rabbits. As the spacer molecule, the 6-carboxymethoxime was used. For the preparation of anti-HSP23 antiserum, the HSP23 was partially purified in the late third instar larvae by ammonium sulfate fractionation and SDS-polyacrylamide gel electrophoresis. These prepared two antibodies were used to quantification of β-ecdysone and HSP23 by the method of radioimmunoassay and immunoblotting respectively. The concentration of β-ecdysone was strikingly increased at the late third instar larva (about from 84 hr after egg deposition) and reached the maximum at prepupa-early pupal stage (114-132 hr). Also, after the induction of HSP23 was started at developmental stage 90 hr, the concentration was sharply increased and then peaked at early pupal stage (130-156 hr). When the synthetic patterns of β-ecdysone and HSP23 were compared, the patterns had a strong resemblance except that synthetic pattern of HSP23 was somewhat followed by that of β-ecdysone. This result suggested at the induction of HSP23 at the normal development was controlled by the β-ecdysone.