A group of 50 patients operated for carcinoma of the colon in June 1980-December 1981 with a follow-up period of min. 2 months-max. 15 months is presented. C.E.A. measurements were taken in all patients pre and post-operatively and then every 2 months in an attempt to establish its diagnostic and prognostic value. In immediate diagnostic and prognostic terms, pre-operative C.E.A. appears to be insignificant. However both pre-operative C.E.A. and C.E.A. at a distance of 6 months were found to be reliable for long term (max. 15 months) prognosis.