Abstract Amineptine and its main metabolite were determined simultaneously in plasma by high-performance liquid chromatography using quinupramine as internal standard. The method comprised adsorption on Extrelut® column from alkaline plasma, elution with diethyl ether—methylene chloride, evaporation in the presence of 0.01 M hydrochloric acid and injection of the acid solution onto a μBondapak C 18 column, using acetonitrile—0.025 M potassium dihydrogenphosphate as mobile phase and ultraviolet detection at 210 nm. Average steady-state concentrations of the two compounds were determined in four patients under treatment regimen (two 100-mg doses of amineptine per day, at 8.00 and 12.00 h). The concentrations determined 20 h after the last dose were undetectable in all cases, whereas the concentrations determined 1 h after the second dose were found to be 780 ± 96 ng ml −1 for amineptine and 690 ± 137 ng ml −1 for its metabolite. The technique can also be applied to whole blood with, if necessary, identification on the basis of the ultraviolet spectrum obtained by photodiode-array detection.