This study is to develop a short term and highly accurate prediction method of renal carcinogenicity based on gene expression profile of rats administrated by carcinogens. We conducted 28 days-repeated dose experiments in male SD rats with ochratoxin A, and the gene expression profiles of renal cortex were analyzed using custom microarrays. Overall design: Experimental design is the two group (control group vs. ochratoxin A treated group). Three biological replicates were performed for each group.