Recent advancement of molecular biology is remarkable. It has been revealed that adenoma carcinoma sequence can be explained by the molecular biological changes, as Vogelstein advocated. The genes on 5q (21-22), 17p (13-1), 18q seem to play an important role for development of colorectal cancers. More recently, APC MCC gene was identified by our colleagues. How does a mutant suppressor gene lead to colon cancer? Following articles by leading researchers in this field might answer this question and solve the problems which we have to face presently.