Screening plays an important role in the diagnosis of both precancerous and cancerous lesions. Screening includes colonoscopy every 10 years, beginning at age 50 in asymptomatic men and women. Other screening tests include flexible sigmoidoscopy (every 5 years), barium enema (every 5 years), and CT colonography (every 5 years). Screening should start at an earlier age and occur more frequently for individuals who are at a higher risk of developing colorectal cancer, such as those with prior history of polyps, prior or family history of colorectal cancer, or history of inflammatory bowel disease. Any suspicion of colorectal cancer warrants a rectal examination and colonoscopy with biopsy of any questionable lesion. Tissue biopsy is the gold standard of diagnosis. Other laboratory studies are done to assess patients’ organ function, as well as imaging of chest and abdomen to help determine tumor staging.