It was well known that calcium sulfate was biocompatible, resorbed rapidly in the body, had potential as a good barrier membrane. Platelet-derived growth factor(PDGF) was one of polypeptide growth factor that had been reported as a biological mediator which regulates activities of wound healing process including the cell proliferation, migration and metabolism. The purpose of this study was to evaluate the effects of a combination of calcium sulfate and PDGF on periodontal ligament cells in vitro to use as a regeneration promoting agent of periodontal tissue. Human periodontal ligament cells were prepared from the premolar tooth extracted for the orthodontic treatment. Cells were cultured in ${alpha}-MEM$ contained with 20% FBS, at the $37^{circ}C$, 100% of humidity, 5% $Co_2$ incubator. Cells were inoculated and cultured into 96 well culture plate with $1{ imes}10^4cells/well$ of ${alpha}-MEM$ for 1 day. After discarding the medium, those cells were cultured in ${alpha}-MEM$ contained with 10% FBS alone(control group), in calcium sulfate(calcium sulfate group), in calcium sulfate treated with 15ng/ml of PDGF-BB(calcium sulfate+PDGF group), in ${alpha}-MEM$ contained with 10% FBS treated with 15ng/ml of PDGF-BB(PDGF group) for 1, 2, 3 day respectively. And then each group was characterized by examining of the cell counting, MTT assay, collagen synthesis. The results were as follows. 1. In the analysis of cell proliferation by cell counting, both calcium sulfate group and calcium sulfate plus PDGF group showed no stastically significant difference compared to control group, but there was stastically significant difference between PDGF group and calcium sulfate group at 1, 2 day(P<0.05). 2. In the analysis of cell proliferation by MTT assay in calcium sulfate extracts, both calcium sulfate group and calcium sulfate plus PDGF group showed no stastically significant difference compared to control group, but there was stastically significant difference between PDGF group and calcium sulfate group at 2, 3 day, and between calcium sulfate plus PDGF group and calcium sulfate group at 2 day(P<O.05). 3. In the analysis of cell proliferation by MTT assay in transwell, both control group and PDGF group showed stastically significant difference compared to both calcium sulfate group and calcium sulfate plus PDGF group at 1 day, but there was no stastically significant difference compared to both calcium sulfate group and calcium sulfate plus PDGF group at 2, 3 day(P(0.05). 4. In the analysis of collagen synthesis by immunoblotting assay in calcium sulfate extracts, high level was detected on calcium sulfate group at 3 day, on calcium sulfate plus PDGF group at 1 day, on PDGF group at 2 day. On the basis of these results, calcium sulfate was biocompatible on the periodontal ligament cells and might have potential possibility as a vehicle of PDGF in the periodontal tissue regeneration.