Colorectal cancer is a major public health problem in the United States. The annual incidence of colorectal cancer is more than 150 000, with approximately 110 000 new cases of colon cancer (tumors above the peritoneal reflection or more than 12 cm proximal to the anal verge) and 45 000 new cases of rectal cancer each year. Over the past 30 years, the population-adjusted incidence has remained constant at approximately 47 cases per 100 000, and thus the number of cases has increased due to population growth. These tumors are predominantly of a single histological type, adenocarcinoma. The average age at presentation is 60 to 65 years. About 75% of the individuals with these cancers will have a primary surgical resection with the hope of complete tumor eradication. Recently, mortality from colorectal cancer has decreased overall, more for rectal than for colon tumors. Despite the high resectability rate and a general improvement in therapy, nearly half of all patients with colorectal cancer still die of metastatic tumor.