The migration and proliferation of periodontal ligament cells are desired goal of periodontal regeneration therapy. PDGF and $TGF-{eta}1$ are well known to regulate the cell activity of mesenchymal origin cell. The purpose of this study was to determine the effects of these growth factors on human gingival fibroblast and periodontal ligament cell actvity, and to identify the regulatory effect of $TGF-{eta}1$ on the response to PDGF by MIT assay. Human gingival fibroblast and periodontal ligament cells were cultured from extracted teeth for non-periodontal reason. Cultured human gingival fibroblast and periodontal ligament cells in vitro were treated with polyperpetide growth factor PDGF and $TGF-{eta}1$ in both a dose and time - dependent manner. Cell morphology were determined by inverted microscope and cell acitivity were determined by MIT assay. The result of this study demonstrated that PDGF and $TGF-{eta}1$ were not changed the morphology of these cell compared with control group. PDGF or $TGF-{eta}1$ increased cell activity of periodontal ligament cell in dose and time dependent manner but gingival fibroblast were decreased to the level of control group at third day. Additionally, incubation with $TGF-{eta}1$ addition to PDGF resulted in a enhanced cell activity of PDGF. Therefore, cell acitivty of gingival fibroblast were not changed compared with control group. This stiudy demonstrates that PDGF and $TGF-{eta}1$ are major mitogens for human periodontal ligament cell in vitro, and $TGF-{eta}1$ is a regulator of cell activity to PDGF in human gingival fibroblast and periodontal ligament cell.