Fibroblasts are major cellular components of gingiva and periodontal ligament. They regulate the healing process after surgery or injury. Recently, many natural medicines, whose advantages are less side effects and possibility of long-term use, have been studied for their capacity, their anti-bacterial and anti-inflammatory effects and regenerative potential of periodontal tissues. Sophorae radix have been traditionally used as an antibacterial and anti-inflammatory drug in oriental medicine. The purpose of present study was to investigate the effects of Sophorae radix extract on cell cycle progression and its molecular mechanism in human gingival fibroblasts. Sophorae radix extracts(100microgram/ml) notably increased cell proliferation and cell activity in the human gingival fibroblasts as compared to non-supplemented controls. There was an increase in the S phase and a decrease in the G1 phase in 100microgram/ml of Sophorae radix extracts group as compared to non-supplemented controls. The level of cyclin E and cdk 2 protein in test group was higher than that of control groups. But that of cyclin D, cdk 4, and cdk 6 was not distinguished from controls. The level of p53 protein in test group was lower than that of controls, whereas that of p21 was not different. The level of pRB protein in test group was higher than that of controls, whereas that of p16 was lower. These results indicate that the increase of cell proliferation by Sophorae radix extracts may be due to the increased expression of cyclin E and cdk 2, and the decreased expression of p53 and p16 in human gingival fibroblasts.