Abstract: The ion-pair reversed phase HPLC was applied to the determination of adrenalin and corticosterone in chiral biotransformation.Activated bacterin was inoculated to the liquid culture medium and cultured for 24 h.Then corticosterone (910 mg·L-1) was added and cultured at pH 5.5 with constant agitation.Samples from the fermented liquor were taken at definite intervals and centrifuged for 10 min at 10 000 r·min-1.The supernatant liquor was taken,filtered through 0.2 μm menbrane and used for HPLC determination.ODS C18 column was used as stationary phase,and a mixture of methanol and 25 mmol·L-1 NaOAc-HOAc buffer containing 4 mmol·L-1 sodium octanesulfonate (15+85) was used at mobile with a flow-rate of 1.0 mL·min-1.UV-detection at 233 nm was used in the determination.Linear relationships between the peak area and the mass concentration of adrenalin and corticosterone were obtained in the ranges of 28-1 800 mg·L-1 and 36-1 350 mg·L-1with their detection limits (S/N=3) of 1.4 mg·L-1 and 2.8 mg·L-1 respectively.Results of recovery test were in the range of 99.3%-100.3%.