There is no specific association established between colorectal cancer and blood group type. In this study, the distribution of ABO and Rh blood groups was studied in 838 patients with colorectal cancer. There was no difference in distribution of ABO blood groups between patients who were Rh+ and Rh-. There was no difference in ABO blood group or Rh factor and tumor location. The highest A/O ratio was found in rectal cancer. Although there was no difference in stage distribution for each ABO blood group, there was a significant difference between the Rh+ and Rh-groups (P <0.037). It is not clear, however, whether the prognosis is different between the two groups since there were more early tumors as well as incurable tumors in the Rh-group. All patients with synchronous cancer were Rh+. Further studies on blood group antigens are needed to elucidate the relationship between these antigens and colorectal cancer.