The findings that high levels of ROS were found in the blood of patients with sporadic CRC and in the normal-appearing rectal mucosa of patients with history of CRC, compared to patients with familial risk of FAP, not only confirm the crucial role of oxidative stress in CRC but also suggest a minor role of ROS when APC expression is completely lost, as in patients with FAP. This evidence concerns the gene APC and colorectal carcinoma.