The value of the simultaneous estimation of serum carcino-embryonic antigen (CEA) and C-reactive protein (CRP) concentrations in staging patients with colorectal neoplasias was evaluated. The study included 95 patients with benign or malignant epithelial tumors of colon and rectum. The simultaneous negative values of CEA and CRP were able to exclude stage D tumors with a specificity of 92.6% (P less than 0.001). Simultaneously positive values of CEA and CRP were able to diagnose stage C or D tumors with a specificity of 92.1% (P less than 0.001). It is concluded that the combination of CEA and CRP tests can substantially contribute to the preoperative staging and assessment of the extent of colorectal cancer.