Abstract: Triptonide,isolated from Tripterygium wilfordii Hcok.,was found to showsignificant antiinflammatory,immunosuppression and antitumor activities.A RP-HPLC methOd wasapplied to determine the plasma concentration of triptonide at different times in rats.Concentration-time curves after iv 0.7,1.4 and 2.8 mg·kg^-1 of triptonide were fitted to a two-compartment openmedel with T_1/2αof 0.167～0.195 h and T_1/2βof 4.95～6.49 h.The area under curves(AUCs)were linearly related to the dosages(r=0.9894).Systematic clearances(CLs) were independent ofdOsages.Mean residence time(MRT) of the three doses was 3.26～5. 14 h by noncompartmental(the statistical moment methed)analyses,The tissue distribution of triptonide in rats appeared to bewide throughout the body.The triptonide levels were high in the lung and liver,mederate in theheart,kidney,spleen and muscle and low in the testis,intestine and brain. Data of the urine and bileexcretion indicated that only a small percent of unchanged triptonide was excreted.Plasma proteinbinding of triptonide rate was about 75%.