Abstract: AIM To study the antifibrotic effects of genistein (GE) and quercetin (QU) on rat hepatic stellate HSC-T6 cell proliferation stimulated with platelet-derived growth factor (PDGF), collagen synthesis and type I procollagen messenger RNA (mRNA) expression stimulated with transforming growth factor β₁ (TGFβ₁). METHODS Cell proliferation was measured by crystal violet staining assay. Collagen synthesis was determined by ³H-proline incorporation assay. Type I procollagen mRNA level was determined by reverse transcription polymerase chain reaction (RT-PCR). RESULTS GE (25-70 μmol·L^-1) and QU (6.25-50 μmol·L^-1) concentration-dependently attenuated PDGF-drive HSC-T6 cell proliferative activity. TGFβ₁- stimulated collagen synthesis was also reduced. This was associated with a decrease of type I procollagen mRNA, indicating an effect at a pretranslational level. CONCLUSION GE and QU may have therapeutic potential against liver fibrosis by regulating PDGF and TGFβ₁ actions.