Abstract: The pharmacokinetics of ³H-N-hydroxycantharidinimide was studied in rats.The results showed that the logarithm of drug concentration in plasma versus time curve after intravenous administration was fitted to a two-compartment open model with first order elimination. The pharmacokinetic parameters are as follows: t 1/2α 0. 067 hr, t 1/2β 2.208 hr, V_d(area)1.237 1/kg, V₁ 0.264 1/kg, Kel 1.470 hr^-1, Cl 0.388 1/hr/kg. The oral plasma level data were adequately fitted to a one-compartment open model with first order absorption and elimination. The pharmacokinetic parameters are as follows: Ka 2.990 hr^-1, Kel 0.257 hr^-1, V_d 1.603 1/kg, t 1/2 2.693 br, T_max 0.90 hr, Cmax 0.745μg/ml, F 94.15%.After intravenous and oral administration, the tissue distribution and the amount excreted in urine, bile and faeces within 24 hours were observed directly in rats. These results revealed that radioactivity was distributed widely in the body and excreted mainly in urine in a fairly rapid rate, which was in agreement with the results of pharmacokinetic analysis.The drug-plasma binding rate was found to be 13.9%.