The purpose of this study was to evaluate the cytotoxic effects of 6 cavity liners in vitro. Human fibroblasts were cultured in ${alpha}$-MEM and each liner was manually mixed and filled in glass ring cylinder ($8{ imes}8mm$ in diameter, in height). The cylinders filled with the liners were placed in the center of the dish (35mm in diameter) containing 3ml of ${alpha}$-MEM. Millipore filters (pore size $0.22{mu}m$) to simulate dentin barrier were also placed between the bottom of cylinder and the dish. Then the culture dishes were stored in 5% $CO_2$ containing incubator for 5 and 10 days at the temperature of $36.6^{circ}C$. The results of the experiments were analyzed by counting the cells in the period of 5 and 10 days respectively, and were assessed by calculating the cell multiplication rate and the relative growth rate. The experiemntal groups and the control group were compared statistically. The results of the study were summarized as follows: 1. The cell number of Zinc oxide-eugenol was $(4.13{pm}1.31){ imes}10^4$ cells/ml at 5 days and $(4.32{pm}1.61){ imes}10^4$ cells/ml at 10 days. 2. The cell number of Cavitec was ($8.35{pm}2.87{ imes}10^4$ cells/ml and $(10.08{pm}5.10){ imes}10^4$ cells/ml at 5 and 10 days respectively. 3. The cell number of Dycal was $(13.56{pm}3.89){ imes}10^4$ cells/ml at 5 days and $(34.75{pm}8.85){ imes}10^4$ cells/ml at 10 days. 4. The cell number of life was $(11.46{pm}3.32){ imes}10^4$ cells/ml and $(21.92{pm}6.18){ imes}10^4$ cells/ml at 5 and 10 days. 5. The cell number of Base cement was $(13.73{pm}3.73){ imes}10^4$ cells/ml and $(36.68{pm}5.20){ imes}10^4$ cells/ml at 5 and 10 days. 6. The cell number of Dentin cement was $(13.58{pm}3.90){ imes}10$ cells/ml and $(66.95{pm}24.09){ imes}10$ cells/ml at 5 and 10 days. 7. The cell multiplication rate of zinc oxide-eugenol cements was significantly less than that of the calcium hydroxide and glass ionomer cement. (P < 0.05)