OBJECTIVE: To investigate the augmentation of microsomal glutathione S-transferase (mGST) preparation using simple organic compounds. METHODS: Rat liver microsomes were isolated using both the polyethyleneGlyco 6000 (PEG6000) and Ca(2+) precipitation methods. Next the mGST activity was measured after incubation with the alkylating agent N-ethylmaleimind (NEM). RESULTS: The baseline mGST activity of rat microsomes was 0.15 after PEG6000 exposure and 0.082 after Ca(2+) precipitation. After NEM treatment mGST activity increased to 1.797 (2.35X) (P<0.01) and 2.375 (4.127X) (P<0.01) respectively followed by purified washing. mGST activation was stimulated maximally by 5-10 mmol/L NEM and occurred rapidly with 1-2 min of co- incubation. CONCLUSION: For both the PEG6000 and Ca(2+) precipitation methods the mGST activity of rat microsomes can be significantly enhanced after exposure to NEM. This enhancement is more prominent with the Ca(2+) precipitation.