The purpose of this study is to evaluate the effects of dentin bonding agents on the fibroblasts cultivated from human pulp tissue. The fibroblasts were cultured in DMEM/10%FBS medium. Whatman filter paper discs (6mm diameter) soaked with $2{mu}l$ of dentin bonding agents were placed on a millipore filter (pore size $0.22{mu}m$) contained in a 50mm Petri dish, and then, exposed for 10 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, 24 hours, 4 days and 7 days in $37.^{circ}C$, 5% $CO_2$ incubator. The results of the experiments were analyzed by counting the cells and measuring the protein contents at 1 day, 4 days and 7 days. The results of this study were as follows: l. CLEARFIL NEW BOND, LITE-FIL BOND, GLUMA 3 Primer and GLUMA 4 Sealer showed cytotoxicity compared to the control group in the cell counts and the protein contents. 2. GLUMA 4 Sealer showed the least cytotoxicity among the three dentin bonding agents. 3. The results of the cell count were simialr to the results of protein content measurement. 4. LITE-FIL BOND exhibited marked cytotoxicity during 1 day, but, the cytotoxicity was slightly reduced after 4 and 7 days. 5. In GLUMA 3 Primer group, it was not possible to count the cell numbers and measure the protein contents, but the degeneration of cells was observed under the inverted phase-contrast microscope.