Abstract: AIM: To investigate the effect of some gene expression in inhibition of celluar malignant transformation by oltipraz. METHODS: Human fetal lung (HFL) treated with cigarette smoking condensate (CSC) and / or oltipraz was extracted for DNA and transfected into Rat-1 cell. C-Ha-ras gene mutation of Rat-1 and transformated Rat-1 cell were analyzed by PCR-RFLP. GST activity and GST-π were examined by colorimetric determination and ELISA. RESULTS: Oltipraz can decrease GST activity and GST-π protein content along with its inhibition of HFL carcinogenesis, but no obvious effect on mP53 gene expression. CONCLUSION: The effects of GST-π and C-Ha-ras gene may be involved in inhibition of cellular malignant transformation by oltipraz.