Yes. Colonoscopy is the most accurate method of diagnosis. It allows direct examination from the rectum through the entire large intestine up to the base of the appendix, permits biopsy and -- at a great cost saving -- removal of polyps.

For cancer of the colon or rectum, the barium enema is highly accurate. But that accuracy is limited to the late -- and incurable -- stage of the disease.

University of Tennessee gastroenterologist Bergein F. Overholt and Yale surgeon Irvin Modlin -- as well as my own experience -- have shown that colonoscopy is the most effective diagnostic technique.

Each year in the U.S., colorectal cancer is found in 140,000 patients, but half of them die because of the late stage at which they are diagnosed. Patients over 40 with colorectal symptoms or hidden blood in the stool should have a colonoscopy. To improve their survival, we must find and remove benign growths before they progress to cancer and find cancerous growths earlier.

Colonoscopy is also of great value in identifying the stage of inflammatory bowel disease, for example, ulcerative colitis or regional enteritis.

A positive finding on barium enema requires colonoscopy for precise identification. A negative barium enema also requires colonoscopy if symptoms persist.

Applied according to risk factors, colonoscopy is cost-effective. No cancer has arisen in 128 patients we have followed for eight years after removal of polyps or cancers.

It is only through broad use of colonoscopy that we will achieve the 85 to 90 percent cure rates that are potentially possible. Colorectal carcinoma is common, curable -- if detected early -- and preventable -- if we remove benign growths.

-- Dr. George F. Gowen director of surgical endoscopy, Pennsylvania Hospital; associate clinical professor of surgery, University of Pennsylvania, Philadelphia

No. When a patient has symptoms that may be caused by disease in the colon -- rectal bleeding, abdominal pain, weight loss, constipation or anemia -- and we don't know just where the problem is, diagnostic evaluation of the colon should be performed. The two basic choices are colonoscopy or X-ray examination. Colonoscopy is of value only for lesions of the colon's mucosal surface (inner lining).

But a barium enema can diagnose lesions not only in the mucosal surface, such as polyps, cancer and inflammatory bowel disease, but also those in the wall of the colon -- benign tumors and endometriosis -- or those outside the colon but pressing on it, such as gynecologic tumors, appendicitis and diverticulitis. So it's effective for a much greater variety of lesions.

Second, the barium enema has a much higher success rate -- at least 95 percent -- in visualizing the entire colon. Colonoscopy fails to visualize the entire colon in about 25 percent of cases.

Third, there's a much higher rate of complications. The most serious -- perforation of the colon -- is much more common with colonoscopy.

Fourth, colonoscopy's cost is three to four times as high. For the several million procedures done annually, replacing X-rays with colonoscopy would add billions to health-care costs.

Furthermore, the advantage in diagnostic accuracy over well-performed double-contrast enemas is very small. For polyps of 1 centimeter in size, which are the significant ones, the difference is minute. It doesn't justify colonoscopy's additional expense and higher complication and failure rates.

-- Dr. Igor Laufer professor of radiology and chief of gastrointestinal radiology, Hospital of the University of Pennsylvania, Philadelphia