Abstract: The composition of the purified HMX/RDX mixture as produced by the combination process w s determined through reverse-phase high performance liquid chromatography with a Lorbax ODS stationary phase and a methanol/ water ( 50/50 ) mobile phase. It has been demonstrated that the method of HMX/RDX composition determination shows many advantages such as rapidity, precision and good reproducibility- and can thus provide a convenient method for the analysis of HMX/RDX commercial products.