Background & Aims: The ability of the bone marrow cells to differentiate into liver, pancreas, and other tissues led to the speculation that these cells might be the source of adult stem cells found in these organs. The present study analyzed whether the bone marrow cells are a source of hepatic oval cells involved in rat liver regeneration induced by 2-acetylaminofluorene (2-AAF) and 70% partial hepatectomy (PHx). Methods: Three groups of mutant F344 dipeptidyl peptidase IV–deficient (DPPIV −) rats were required for the study. Groups A and B received the mitotic inhibitor monocrotaline, followed by male F344 (DPPIV +) bone marrow transplantation. Next, group A received PHx only, while group B received the 2-AAF/PHx required for the oval cell activation. The last group C was used to analyze the effects of monocrotaline on transplanted bone marrow cells. These rats underwent transplantation with bone marrow cells and were then treated with monocrotaline. Subsequently, the animals were treated with 2-AAF/PHx. Results: In group A, DPPIV + hepatocytes were found in the liver. Group B showed that approximately 20% of the oval cell population expressed both donor marker (DPPIV) and α-fetoprotein, and some differentiated into hepatocytes. In contrast, animals in group C failed to significantly induce oval cells with the donor DPPIV antigen. In addition, X/Y-chromosome analysis revealed that fusion was not contributing to differentiation of donor-derived oval cells. Conclusions: Our results suggest that under certain physiologic conditions, a portion of hepatic stem cells might arise from the bone marrow and can differentiate into hepatocytes.