Serum TPS and CEA levels were measured in 173 cancer patients with various disease stages. The patients were divided into 4 groups: preoperative group, 16 patients in whom TPS and CEA were measured pre- and postoperatively; group I, 66 newly diagnosed patients up to 40 days post surgery; group II, 86 patients whose blood was taken 40-365 days post surgery, and group III, 47 patients on long-term follow-up in whom blood was taken more than one year after surgery. The median preoperative TPS levels were significantly higher (p<0.01) than the postoperative levels. Patients with Dukes' D had significantly higher TPS (p<0.01) and CEA levels as compared to patients with Dukes' B or C. For both Dukes' B and C stages there was a significant increase in median TPS level between group I and II and III. There was no similar increase in median CEA level. Serial measurements in individual patients show a significant increase in TPS levels between groups I, II and III. In Dukes' D patients, individual TPS levels decreased in response to therapy. There was a significant correlation between TPS and CEA levels. These results suggest that TPS measurement is additive to CEA in follow-up of asymptomatic patients, and to monitor response to therapy in patients with metastatic disease.