&NA;Preoperative levels of perchloric acid extractable plasma CEA were measured in 911 patients with complaints of the digestive system. A final diagnosis of benign disease was made for 579 patients; 332 patients were found to have cancer. Data for the preoperative CEA values were examined for clinical significance as an aide to diagnosis, preoperative disease staging, and prognosis.The results of our analysis support the conclusions of many investigators that the CEA assay is not a clinically useful diagnostic test, but it shows limited value in preoperative staging and a somewhat stronger correlation with prognosis.