The development of a high-sensitive cytotoxic detection system using heat-shock proteins (HSP)70B promoter was discussed. Human liver carcinoma cell line was grown in DMEM at 37 °C in a humidified atmosphere with 5% CO 2. Cell viability was evaluated by quantification of DNA performed by using Cyquant Proliferation Assay kit. Subsequent sequencing revealed that transcriptional starting site was mapped at - 110 bp from the translational starting site in HepG2. These results suggests that the effect of low concentration of cadmium chloride on cytotoxicity could be detected by luciferase analysis using a part of HASP70B promoter.