tiple alterations affecting DNA mismatch repair genes, oncogenes, and tumorsuppressor genes, and that common and uncommon genetic changes exist for esophageal, gastric, and colorectal carcinomas. In addition to these genetic changes, the majority of gastrointestinal cancers express telomerase activity, with overexpression of telomerase RNA, indicating a powerful addi­ tional tool for early detection of gastrointestinal cancer. By transferring these basic observations to the clinic, we now are able to make accurate cancer diagnoses, thus determing the grade of malignancy and patient prognosis. We also can identify patients at high risk for developing cancer and create new therapeutic approaches. In fact, we have routinely implemented a new molecular diagnosis strategy at the Hiroshima City Medi­ cal Association Clinical Laboratory since August 1993.