Simple and rapid procedures were developed for the quantification of amfepramone hydrochloride and diazepam and mazindol and diazepam in tablets using high performance liquid chromatography (HPLC) with UV detection. These techniques provided conditions for the separation of each active ingredient from the complex matrices of the dosage forms by dilution or extraction in methanol. Isocratic reversed phase chromatography was performed using acetonitrile, methanol, and aqueous 0,1% ammonium carbonate (70:10:20, v/v/v) as a mobile phase, Radial-Pak C18column (100 × 8 mm id, 4μm), a column temperature of 25 ± 1°C and detection at 255 nm. The calibration curves were linear over a wide concentration range (100–1000 μg.mL−1to amfepramone hydrochloride and mazindol and 10–100 μg.mL−1to diazepam) with good correlation factors of 0.9978, 0.9956 and 0.9997 for amfepramone hydrochloride, mazindol, and diazepam, respectively.