To evaluate the oxidative stress in patients with colorectal cancer and to investigate the relationship between oxidative stress and colorectal cancer. Methods Seventy-six subjects were divided into two groups (36 colorectal cancerpatients as the study group and 40 normal healthy individuals as the control group). Their protein oxidation, DNA damage, lipid peroxidation and antioxidants, vitamin C, vitamin E, glutathione (GSH), and antioxidative enzymes in serum were detected. Results The levels of protein carbonyl and advanced oxidation protein products (AOPP) were significantly higher in the study group than in the control group (P