OBJECTIVE The purpose of this study is to identify morphologic parameters of colorectal adenocarcinoma which may be of influence in the increase of preoperatory CEA serum levels. METHODS This study includes 127 patients on whom colectomy was performed. Twenty-eight morphologic parameters were analyzed in each surgical specimen. Serum determinations were made by enzymatic immunoassay. A multivariate study (logistic regression analysis) was made. Independent risk factors for CEA serum elevation were Cytologic Atypia (odd ratio: 2.85) Infiltrative Growth Pattern (odd ratio: 2.91) and the presence of tumoral cell infiltration directly among adipocytes (odd ratio: 2.62). When clinical variables (age, sex, tumor location, perforation, occlusion, hepatic metastases and peritoneal carcinomatosis) were added the infiltrative growth pattern (odd ratio: 3.12) and cytologic atypia persisted as independent risk factors, together with the clinical variable Hepatic Metastases (odd ratio: 24.84). CONCLUSIONS In our series the morphologic variables Infiltrative Growth Pattern and Cytologic Atypia are independently related with CEA serum increase and are not influenced by the variable Hepatic Metastases.