A solid-phase method for the extraction of simmondsin from plasma was developed along with a liquid chromatographic method for the quantitative measurement of this compound. The extraction of simmondsin is realised with activated carbon. Chromatography is performed on a 25 x 0.46 cm I.D. RP-18, 5-micron HPLC column with a water-methanol (85:15, v/v) mobile phase and ultraviolet absorbance detection at 217 nm. The limit of detection is 100 ng (using 1 ml of plasma). The linear quantitation range is 0.1-200 micrograms/ml.