Colorectal cancer is a leading type of cancer and a leading cause of cancer death in the United States. Screening for colorectal cancer can lower the risk for dying of colorectal cancer by finding growths (polyps) before they become cancer or by finding cancer at an early, curable stage. Available screening tests include the fecal occult blood test (FOBT) and colonoscopy. Fecal occult blood testing usually uses a chemical reaction on a paper card to find traces of blood that can leak from polyps and cancer into the stool. Colonoscopy involves looking for polyps and cancer in the colon through a flexible tube. Fecal occult blood testing is simpler and less expensive than colonoscopy, and research shows it can reduce the risk for dying of colorectal cancer. However, for the test to be effective, it must be performed by collecting several stool samples at home, and a positive result must be followed by colonoscopy to look for the source of the blood. It is not known if doctors follow these standards in practice.