A primary objective in the treatment of periodontal disease is the regeneration of the mineralized and soft connective tissue. PDL cells produce mineralized nodules in vitro which is one of the important functions of PDL cells for regenerative therapy. The purpose of this study was to investigate the effects of estradiol on mineralized nodule formation by human PDL cells. PDL cells were obtained from healthy donors and maintained in DMEM with 10% fetal bovine serum. Serum-free medium was used when the effects of estradiol were tested. ALP activity in the supernatant of cells disrupted by sonication was analyzed spectrophotometrically. The formation of mineralized nodules was assessed by staining the PDL cells with alizarine red and counting the number of nodules. at Estradiol 20 ng/ml significantly enhanced the ALP activity and mineralized nodule formation compared to the control. These results suggested that estrogen status may modify the regenerative activity of periodontal tissue.