BACKGROUND: Even though careful techniques is utilized and proper concentration of local anesthetics are used, tissue toxicity is common. METHOD: The fibroblast cell lines (NUGM) was exposed with each concentration of 10(-6), 10(-5), 10(-4) M lidocaine and bupivacaine in culture media for 24 hours. Glucose consumption rate and LDH activity in cultured media were measured for using as indicator of cellular damage on 0. 24, 48, 72 hours. By using that, we calculated the trend lines of the change of glucose consumption rate and LDH (lactic dehydrogenase) activity. On the trend lines, we searched out for decreasing time to 1/2 of glucose concentration and increasing time to 2 times of LDH activity compared to control. RESULTS: 1) In control group, Decreasing time to 1/2 of glucose concentration was 236.0 hours (p<0.05) and increasing time to 2 times of LDH activity was 1168.6 hours (p<0.05). 2) At each concentration of 10 6, 10 5, 10 4 M lidocaine, decreasing time to 1/2 of glucose concentration was 873.7 (370%), 938.7 (398%), 1101.6 (467%) hours compared with 236.0 (100%) hours of control (p<0.05) and then increasing time to 2 times of LDH activity was 135.1 (12%), 85.6 (7%), 93.9 (8%) hours when compared with 1168.6 (100%) hours of control (p<0.05). 3) At each concentration of 10(-6), 10(-5), 10(-4) M bupivacaine, decreasing time to 1/2 of glucose concentration was 706.7 (299%), 948.1 (402%), 1018.2 (431%) hours when compared with 236.0 (100%) hours of control (p<0.05) and then increasing time to 2 times of LDH activity was 111.6 (10%), 69.5 (6%), 59.1 (5%) hours when compared with 1168.6 (100%) hours of control (p<0.05). 4) On light microscopy, cells are showed destruction in each concentration of 10(-6), 10(-5), 10(-4) M lidocaine and bupivacaine with dose dependent fashion. CONCLUSIONS: 1) Glucose consumption rate and LDH activity in cultured media could be used as a useful index of cellular destruction by toxic effect on cultured cell. 2) Even at any concentration of lidocaine and bupivacaine could be toxic on cell. With all of above results, cell-line on 3 demensional cultured method could be use as another method for determining of cellular toxicity of local anesthetics.