Abstract: BACKGROUND ＆ AIM: We investigated the gene expression profiles of primary mouse hepatocyte culture induced by 13 chemicals by using DNA microarray. We then used clustered analysis on the gene expression profiles, and then tried to classify chemicals based on the level of the genome response, so that a relation could be made between the classification of chemicals and its gene expression profiles. MATERIAL AND METHODS: Primary mouse hepatocyte culture was treated with 30％ of the lethal dose of 13 chemicals. 24 hours after treatment, RNA was extracted and reverse transcribed to cDNA. The cDNA were detected by DNA microarray. RESULTS: By using average- linkage hierarchical clustered analysis, 13 chemicals were classified into 3 groups. CONCLUSION: Classifying chemicals by gene expression profiles, so as to classify them relative to their toxic action then to study their toxicity mechanism and to predict the toxicity of unknown chemicals is a worthwhile and promising research direction.

Key words: DNA microarray;gene expression profiles, toxicogenomics;clustered analysis