Administering of 2-acetylaminofluorene (2-AAF) before a two-thirds partial hepatectomy (PHx) results in suppression of hepatocyte proliferation and stimulation of oval cell proliferation. The objectives of this study was to examine the oval cell behaviour and associated transforming growth factor-β1 (TGF-β1) protein expression by combining 2-AAF with selective hepatic damage caused by PHx. We also studied the temporal relationship between TGF-β1 expression, and proliferation and apoptosis of oval cells. Oval cells emerged from the portal areas and became more numerous with time fanning out into the periportal and midzonal hepatic parenchyma. Both smooth muscle actin (SMA) and TGF-β1 immunostain revealed that TGF-β1-positive cells were SMA-positive hepatic stellate cells (HSCs). Coinciding with the proliferation of oval cells, an increase expression of TGF-β1 produced by SMA-positive HSCs was observed, thereafter apoptosis of oval cells reached its peak. This result implicated that TGF-β1 produced by HSCs is intimately associated with proliferation and apoptosis of oval cells, and plays a role in the cessation of oval cell activation and remodeling of liver parenchyma in 2-AAF induced liver regeneration.