With few exceptions, epidemiological studies have found that individuals who take nonsteroidal antiinflammatory drugs (NSAIDs) have a reduced risk of colorectal adenomas and carcinoma. Similarly, randomized studies in patients with familial adenomatous polyposis have uniformly found that NSAIDs can lead to polyp regression and prevention of new polyps, and trials in patients with sporadic adenomas document that aspirin reduces the risk of adenoma recurrence. Together these data provide convincing evidence for the chemopreventive efficacy ofNSAIDs in the large bowel.