Colorectal cancer (cancer of the colon [large intestine] or rectum) is the third most common cancer in men and women. When it is discovered in its early stages, colon cancer is treated with surgery and often cured. However, many individuals with colon cancer have no symptoms until the disease reaches an advanced stage, such as metastasizing (spreading) to other organs. Colorectal cancer is the second leading cause of cancer deaths (after lung cancer) in the United States. Testing persons without signs or symptoms of colon cancer is called screening. Screening for colon cancer is recommended for everyone older than 50 years and especially for individuals who have significant risk factors. The December 17, 2008, issue of JAMA includes an article reporting that cigarette smoking is significantly associated with the occurrence of colorectal cancer. This Patient Page is based on one previously published in the September 27, 2006, issue of JAMA.