Abstract: The profile of the major metabolites of primaquine produced by in vitro liver microso-mal metabolism was investigated with silica gel thin-layer and high performance liquid chro-matography (HPLC) analysis.The results indicated that the liver microsomal metabolism could simultaneously produce both 5-OH PQ (quinoline ring oxidation product) and CPQ (side-chain oxidative deamination product).However,the quantitative comparative study of microsomal metabolism showed that the production of 5-OH PQ was far much higher than that of CPQ.