The initial events required for periodontal regeneration is the attachment, spreading, and proliferation of appropriated cells at the healing sites. These have been reported that minocycline stimulates the attachment of periodontal ligament cells, and also $TGF-{eta}1$ enhances the proliferation of periodontal ligament cells. The purpose of the present study was to evaluate the effects of $TGF-{eta}1$ on the cellular activity of minocycline treated human periodontal ligament cells. Periodontal ligament cells were obtained from the explants of healthy periodontal ligaments of extracted 3rd molars or premolar teeth extracted from the patients for orthodontic treatment. The cells were cultured in minimal essential medium(${alpha}-MEM$) supplemented with 10.000units/ml penicillin, $10,000{mu}g/ml$ streptomycin and 10% FBS(fetal bovine serum) at $37^{circ}C$ in a humidified atmosphere of 5% carbon dioxide and the 5th to the 8th passages of the cells were used. To evaluate the effect of minocycline on cell attachment, the cells were seeded at a cell density of $1.5{ imes}10^4$ cells/well in 24-well culture plates and treated with $20{mu}g/ml$ and $100{mu}g/ml$ of minocycline for 1.5 h. After trypsinization, the cells were counted with hemocytometer and were taken photographs for observation of cellular morphology. To evaluate the effect of $TGF-{eta}1$ on minocycline-pretreated periodontal ligament cells, the cells were seeded at a cell density of $1{ imes}10^4$ cells/ well in 24-well culture plates and treated with $20{mu}g/ml$ and $100{mu}g/ml$ of minocycline for 1.5 h. After incubation, 1 and 10ng/ml of $rh-TGF-{eta}1$ were also added to the each well and incubated for 1 and 2 days, respectively. Then, MTT assay, DNA synthesis($^3H-thymidine;assay$), and protein and collagen assay(3H-proline assay) were carried out. In the MIT assay, after 200ul MTT solutionlconeentration of 5mg/ml) were added to the each well of the 24-well plates and incubated for 3 hours, and 200 ul DMSO were added so as to dissolve insoluble blue formazan crystals which was formed in incubated period. Then it read plates on a ELISA reader. For mitogenic assay, 1 uCi/ml $^3H-thymidine$ was added to each well for the final 2 hours of the incubation periods. After labeling, the wells were washed 3 times with ice cold PBS and 4 times with 5% TCA to remove unincorporated label and precipitate the cellular DNA. DNA, with the incorporated $^3H-thymidine$, was solubilized with 500 ul of 0.1% NaOH/0.1% SDS. A 250 ul aliquot was removed from each well and placed in a scintillation vial with 4ml of scintillation cocktail. Using an liguid scintillation counter, counts per minute(CPM) were determined for each samples. 3 uCi/ml $^3H-proline$ was added to each well for the final 4 hours of the incubation periods and total protein and percent collagen synthesis were carried out. The results indicate that minocycline treated group with $100{mu}g/ml$ concentration for 1.5 hours significantly increased than that of control in cell attachment, and cell process is also evident compared with that of control in cell morphology, and the cellular activity and DNA synthesis rate of cells treated minocycline and $TGF-{eta}1$ significantly increased than that of control values, but were below to values of the $TGF-{eta}1$ only treated group in MIT assay and $^3H-thymidine;assay$, and the total protein synthesis of minocycline and $TGF-{eta}1$ treated group also significantly increased than that of control values, but the percent collagen synthesis of tested group significantly decreased to compared with control. On the above the findings, the tested group of minocycline and $TGF-{eta}1$ did not increase the ..