Abstract: A RP-HPLC method was developed to determine the concentrations of sinomenine HCl in serum and urine and its pharmacokinetics was studied in healthy volunteers. C₁₈H₃₇ column was eluted with the mobile phase of acetonitrile—0.01 mol·L^-1 sodium phosphate monobasic—N,N,N',N'-tetramethylenediamine (46∶54∶0.22 v/v, pH 6.9) and the utraviolet absorbance was monitored at 263 nm. Triazolan was used as internal standard. The calibration curves were linear in the range of 6～480 ng·ml^-1 in serum and 0.06～3 μg·ml^-1 in urine, with mean recoveries of 75.46% and 91.38% respectively. The lowest detectable limits were 4 ng·ml^-1 in serum and 40 ng·ml^-1 in urine and the RSD for the intra-day and interday were less than 5%.A single oral dose of 80 mg sinomenine HCl tablet was given to 8 healthy male volunteers. The concentrations of sinomenine HCl in serum and urine were determined. The serum concentration—time curve was found to fit a two-compartment open model with first order elimination. The pharmacokinetic parameters were: T_1/2α 0.791±0.491 h, T_1/2β 9.397±2.425 h, T_max 1.040±0.274 h, C_max 246.604±71.165 ng·ml^-1, AUC 2651.158±1039.050 ng·h·ml^-1,CL 0.033±0.010 ng·ml^-1.