Cyclooxygenase-2 (COX-2) inhibitors comprise a group of compounds that show promise as cancer preventives. COX-2 is an inducible enzyme that catalyzes the rate-limiting step in the synthesis of prostaglandins from arachidonic acid. The anti-inflammatory effects of aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs) are a result of their inhibition of this enzyme. A role for this enzyme in cancer development was first hypothesized when it was noted that people who ingest NSAIDs regularly for long periods of time have a significantly reduced risk of colon cancer (1) . Subsequently COX-2 was found to be expressed at high levels in about one-half of colorectal adenomas and most colorectal adenocarcinomas (2) . And more importantly, NSAIDs and other COX-2 inhibitors significantly reduced colon tumor number in both animal (3 ,4) , and clinical studies (5) .
