The aim of this research was to determine possibility of qualitative analysis of diazepine derivatives: alprazolam, medazepam, chlordiazepoxid in the mixture. The high performance liquid chromatography was used for the investigation, the reagents--tablets of alprazolam, medazepam, chlordiazepoxid. It was found out that the most acceptable eluent for the analysis of the mixture by high pressure liquid chromatography is phosphate buffer, containing 0.02 M penthanesulfonic acid:etannitrile (55:45) (pH=3.5). The optimal wavelength for identification of the drugs in the mixture is 254 nm.