The purpose of the present study is to evaluate the relationship between the levels of tumor markers, such as carcinogen-embryonic antigen (CEA) and CA 19-9 antigen, determined in blood serum (sCEA and sCA 19-9) and in peritoneal fluid obtained during surgery (pCEA and pCA 19-9), and the stage of colorectal cancer, including the presence of tumor cells in peritoneal fluid cytology. This evidence concerns the gene CEACAM5 and colorectal cancer.