The causes of colorectal carcinoma are multifactorial. Numerous lines of epidemiologic evidence support the role of dietary factors, with strong associations revealed for folate and calcium, more equivocal evidence exists for dietary antioxidants. Lifestyle factors such as physical activity, alcohol in-take, and tobacco use are also positively correlated with the risk of colorectal carcinoma. Health services research examines epidemiologic issues,clinical evidence regarding prevention and treatment, patient preferences,and other factors with the goal of improving the quality of care. Observations based on epidemiologic studies and health services research will in the future provide the basis for reducing personal and social burdens caused by colorectal carcinoma.