Cyclooxygenase 2 (COX2) is an inducible enzyme synthesizing prostaglandins from arachidonic acid, which is thought to play an important role in colorectal carcinogenesis. Since the COX2 polymorphisms, if functional, may modify the carcinogenesis pathway, the associations between the reported polymorphisms and colorectal cancer risk were examined in a hospital-based case-control study. Six polymorphisms of the gene encoding COX2 were genotyped for 241 non-cancer individuals (controls) and 148 colorectal cancer patients (74 colon cancer, 73 rectal cancer, and 1 colorectal cancer date, 22 polymorphisms including the above six have been reported for COX2. The other polymorphisms remain to be examined.