Acute-phase reactant proteins have been considered in searching for new biochemical tumor markers useful at initial diagnosis, staging and monitoring of colorectal cancer. In this study, we aimed to determine the role of acute-phase reactant proteins in combination with carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) at the preoperative staging of colorectal cancer. In 22 patients with cancers of the colon and rectum and in 9 control patients without cancer, the serum levels of CEA, CA 19-9, C-reactive protein (CRP), alpha(1)-antitrypsin (AAT) and alpha(1)-acid glycoprotein (AAG) were measured. While statistical analysis did not show significant correlations between serum CEA, AAT and CRP levels with the stage of disease, the significant correlations between serum CA 19-9 and AAG concentrations with the extent of cancer were detected (p less than or equal to 0.0197 and p less than or equal to 0.0378, respectively). Multivariate discriminant analysis gave a final prognostic model that included serum CA 19-9 and AAG levels with a significance of p less than or equal to 0.0089. The Linear regression analysis also gave a form of (Stage=0.04667+0.0077xCA 19-9+0.0068xAAG) for staging. We considered that the serum AAG levels, in combination with serum CA 19-9 concentrations may have an important role in the preoperative staging of colorectal cancer.