We examined the incidence of proliferative lesions, hyperplastic nodules and altered hepatic foci, in male F344 rat liver, to determine their preneoplastic potential during dichloroacetic acid (DCA)-induced hepatocarcinogenesis. Immunohistochemical and image analysis methods were used to detect the expression of 6 histochemical markers of neoplastic cells; p21 ras, p39 c-jun, p55 c-fos, aldehyde dehydrogenase (ALDH), glutathione s-transferase (GST-p), and alpha fetoprotein (AFP) during DCA-induced hepatocarcinogenesis. Our results were consistent with our previous data and suggested that the hyperplastic nodules, rather than altered hepatic foci, is a putative preneoplastic lesion during DCA-induced hepatocarcinogenesis in the male F344 rat.