Résumé : A sensitive and accurate procedure based on an alkaloid extraction coupled to an HPLC-UV-MS determination has been developed for the separation and quantification of the major aporphines in Cassytha filiformis. The extraction step and the liquid chromatography conditions were optimized in order to improve the selectivity of the method. The HPLC mobile phase consisted of a mixture of water containing 10 mM ammonium acetate adjusted to pH 3 with acetic acid-acetonitrile (90: 10, v/v) (A) and acetonitrile (B) used in a gradient mode (0 to 40%). The stationary phase was an RP-select B (5 micro m) column. The method was completely validated using cassythine, one of the major aporphines in our samples, as reference standard and successfully applied to the determination of these pharmacologically interesting aporphines in seven different batches of C. filiformis. The detection and quantitation limits of cassythine were found to be 13 and 20 micrograms/mL, respectively. The results showed variations in the total alkaloid content in samples from 0.11 to 0.43%.