To investigate the cytotoxicity of Korean traditional fermented soybean products using the MTT assay, we extracted soybean, Kanjang, Doenjang, Kochujang, and Chongkukjang with water, methanol, and hexane. Primary testing of cytotoxicity of 14 extracts was done for P388D1(mouse lympoid neoplasm) and L1210(mouse leukemia) cell lines. Doenjang methanol extract, Kochujang hexane extract, Chongkukjang methanol extract, and Chongkukjang hexane extract showed cytotoxicity of 86.1, 94.3, 83. 6, and 81.1%, respectively against P388D1, and showed cytotoxicity of 69.4, 96.9, 51.4, and 95.1%, respectively against L1210. All the other extracts showed less than 50% cytotoxicity. Methanol extracts of Doenjang and Chongkukjang showed dose-dependent cytotoxicity against P388DI, L1210, SNU-16 (human stomach cancer), HepG2(human hepatic cancer), WiDr(human colon cancer) cell lines, and IC$_{50}$ of Doenjang methanol extract was 67.7, 90.4, 1338.0, 706.4, and 371.2 $\mu$g/ml, respectively, and IC$_{50}$ of Chongkukjang methanol extract was 107.1, 228.3, 756.2, 1346.0, and 327.0 $\mu$g/ml, respectively.