It is widely believed that DNA synthesis and expressions of smooth muscle a actin and TGF-beta are all together increased in activated hepatic stellate cells both in vitro and in vivo. Our previous reports disclosed that these increases did not always coexist under experimental conditions. Liver necrosis was induced in rats by oral administration of carbon tetrachloride. Hepatic stellate cells were isolated from these rats 2 days later. When these cells were cultured on plastic dishes for 3 days, they showed marked DNA synthesis and smooth muscle alpha actin and TGF-beta mRNA expressions assessed by H-3-thymidine incorporation and Northern blotting, respectively. In the cells further cultured for 7 days, the DNA synthesis was decreased, whereas both smooth muscle cy actin and TGF-beta mRNA expressions were increased, compared to the cells cultured for 3 days. The cells cultured for 10 days showed apoptotic nuclei positive for nick-end labeling, and DNA extracted from the cells revealed laddering patterns on agarose gels by electrophoresis. Apoptotic nuclei were also immunohistochemically found in stellate cells in the liver of rats 4 days after the intoxication We conclude that apoptosis developed in activated hepatic stellate cells both in vitro and in vivo, and this may contribute to the discrepancy between DNA synthesis and cellular functions of the cells.