Glutathione S-transferase (GST) is a conjugation enzyme in the metabolism of exogenous and endi!genous lipophilic compounds for their excretion and detoxification. Acidic isozyme of GST-P, has been recognized as a preneoplastic marker in the experimental hyperplastic nodules of rats. However, the role of the human counterpart GST-π, needs to be elucidated yet. In the present study, the activities of GST and the expression of GST-π were monitored in the human hepatocellular carcinoma (HCCl tissues in comparison with those of normal control tissues. The activities of the cytosolic GST in human HCC tissue were lower than those in the control liver tiscues (p<0.01), while the amount of GST-π measured by ELISA was higher in the human HCC tissues. And the Western blat analysis revealed that GST-π was expressed only in the human HCC tissues. In Sprague Dawley rat hepatocarcinogenic model after Solt and Farber, the activities of cytosolic GST in the liver tissues were shown to be increased in the time function after carcinogen treatment in parallel with the increase of GST-P expressian. Moreover the hyperplastic nodules of rat fiver tissues were identified as GST-P positive foci immunohistochemically. In conclusion, the expression of GST-π in human HCC tissues and of GST-P in the hyperplastic nodules of rat hepatocarcinogenic model, indicates its possible role as a preneoplastic or neoplastic marker either in the experimental cancer model or in the human cancer tissues.