DNA chips can be used for many different purposes, most prominently to measure levels of gene expression for tens of thousands of genes simultaneously. Some of the possible clinical applications of DNA chips for liver diseases are studied in our laboratory. Expression profiles of liver diseases were examined by SAGE (serial analysis of gene expression), and many new transcripts were found in the SAGE libraries. The SAGE information is important to make DNA chips for the analysis of liver diseases. Expression profiles of 26 patients with chronic hepatitis and 10 patients with hepatocellular carcinoma were analyzed by DNA chips. The analyses revealed new information about liver disease. These results imply a DNA chip may be a good tool in routine clinical settings in the near future.