Colorectal cancer (CRC) is a common cancer in the more developed Western countries. This paper aims to give a review of the established or suspected and potentially modifiable risk factors for CRC. Increased BMI, physical inactivity, tobacco smoking and high alcohol consumption are strongly implicated factors. The precise dietary patterns associated with increased risk are less clear. Use of NSAIDs as well as postmenopausal hormones seems to be associated with a substantially reduced risk of CRC. Altogether, the evidence indicates that primary prevention of CRC is feasible.