SummaryTransforming growth factorb1 (TGFb1) is considered to be the principal contributor to liver fibrosis. So in this study the ribozymes against TGFb1 were designed. The in vitro cleavage activities of the ribozymes were assayed through incubation of 32 p-labeled target RNAs and 32 p-labeled ribozymes in different conditions. HSC-T6 cells were transfected with the eukaryotic constructs encoding ribozyme and disable ribozyme, then the stable cell clones were used to evaluate its antifibrotic characteristic through the effect of ribozyme on biological character of activated hepatic stellate cells (HSCs). The results demonstrated that two ribozymes (Rz803 and Rz1395) could cleave target RNAs into expected products effectively, Rz803 possessed better cleavage activity in vitro. Stable transfection of Rz803 into activated HSCs reduced TGFb1 expression in mRNA and protein level efficiently. The further studies demonstrated that Rz803 reduced deposition of collagen I, suppressed HSC proliferation, but had no effect on HSC activation in transfected HSC-T6 cells. Therefore, it indicated that Rz803 could reverse the character of activated HSCs by downregulating TGFb1 expression efficiently and diminishing TGFb1 signaling underlying activation of hepatic stellate cells. As the consequence, it would provide a potential therapeutic approach for liver fibrosis. IUBMB Life, 57: 31-39, 2005 Keywords RNA, catalytic; transforming growth factorb1, hepatic stellate cell; Character Introduction: