Deletion was compared in the region of common deletion of mitochondria) DNA by PCR analysis in tumors and paired adjacent tissue to tumor from Korean patients. In 10 cases out of 16 tumors, more deletion species were found in tumor region, while there was no difference in remaining 6 cases. There were variations of deletions among tumor tissues, and between tumor and paired adjacent tissue of each patient. Major deletion of tumor tissue was 1,400 bp, in colon, thyroid, and ovary, 400 bp in breast, gall bladder, and lung, and 700 bp in stomach, which was similar to that of adjacent tissue to tumor.