Although proliferation of oval cells is often observed during the early stages of chemical hepatocarcinogenesis, the role of these putative hepatic stem cells during the neoplastic process is unknown. In earlier studies our laboratory showed that feeding a choline-deficient (CD) diet containing 0.05% 2-acetylaminofluorene (CD-AAF) to rats produced three subpopulations of oval cells that antigenically resemble biliary duct cells, fetal liver cells, and transitional cells. In the present investigation we have employed a semiallogeneic transplantation protocol in order to study the fate of these nonparenchymal epithelial cells (NPEC) beyond the 4-week endpoint imposed by the lethality of CD-AAF diet. An enriched NPEC suspension containing [gamma]-glutamyl-transpeptidase (GGT)-positive oval cells (> 75%) was isolated from ACI rats maintained on CD-AAF diet for 3 weeks. The donor cells were transplanted via the portal vein into livers of male F1 progeny (LExACI) that had been fed a CD diet for 7 days prior to receiving a partial hepatectomy and the cell suspension. Host rats were then fed either a CD or choline-supplemented (CS) diet for 12 weeks and killed. Colonies of donor-derived cells identified in frozen sections by their lack of reactivity with ACI anti-LE alloantiserum in indirect immunofluorescence (IF) assays were only observed in rats continuously fed the CD diet. Histochemical analysis indicated that the donor-derived colonies expressed GGT, a preneoplastic marker for liver cancer.