Abstract: A reversed phase high performance liquid chromatographic method for the assay of midecamycin was developed. The method used a Hitachi Gel 3050 column at 50℃ and a mobile phase of methanol—0.01 mol/L phos- phate buffer solution at pH 5.8 (45:55). The column effluent was monitored Zat 231nm. SF-837A₁, leucomycin A₆ and minor components could be separated in less than 15min. The retention times of SF-837A₁ and leucomycin A₆ are 7 and 10 min respectively. The method is very simple and rapid.