We reported in this manuscript that TGF-β1 induces apoptosis in AML12 murine hepatocytes, which is associated with the activation of p38 MAPK signaling pathway. SB202190, a specific inhibitor of p38 MAPK, strongly inhibited the TGF-β1-induced apoptosis and PAI-1 promoter activity. Treatment of cells with TGF-β1 activates p38. Furthermore, over-expression of dominant negative mutant p38 also reduced the TGF-β1-induced apoptosis. The data indicate that the activation of p38 is involved in TGF-β1-mediated gene expression and apoptosis.