The purpose of the present study was to evaluate the effect of platelet - derived growth factor(PDGF) - BB and insulin - like growth factor(IGF) - 1, Centella Asiatica, and Zea Mays L. on the mitogenic activity of PDL cells from healthy and RPP patients. Combination of PDGF - BB and IGF - 1, Centella Asiatica, and Zea Mays L. were treated on PDL cells and the mitogenic effects were meaured by quantitative assay of methyl - $^3H$ - thymidine incorporation during DNA synthesis. Combination of PDGF - BB and IGF - 1 enhenced the mitogenic effects of both healthy and RPP PDL cells, however, the effect was less pronounced on RPP PDL cells. In cases of Centella Asiatica and Zea Mays L., no mitogenic effect on healthy PDL cells could be noticed.