Colorectal cancer is one of the most common types of cancer. Screening prevents colorectal cancer deaths by 1) finding and removing noncancerous outgrowths of the colon or rectum [polyps] before they become cancer and 2) finding cancer at early, curable stages. Available screening tests include fecal occult blood testing (FOBT), sigmoidoscopy, colonoscopy, and barium enema. Fecal occult blood testing uses a chemical reaction to find traces of blood in stool. Polyps and cancer can cause blood to leak into the stool, so a positive result on FOBT suggests the need for further testing. Sigmoidoscopy involves looking into the rectum and lower colon through a flexible tube-shaped instrument; colonoscopy uses a similar but longer instrument to look at the entire length of the colon. Doctors can take samples of the colon (biopsies) and remove polyps during both procedures. Barium enema involves taking x-rays of the abdomen after putting barium (a material that appears white on x-ray) into a person's colon by enema. If x-rays indicate a lesion in the colon, follow-up testing with colonoscopy is needed. Fecal occult blood testing is inexpensive, colonoscopy is expensive, and sigmoidoscopy and barium enema are moderately priced.