Extensive follow-up investigations were done in 1978 in 135 patients, most of whom had been operated for colo-rectal carcinoma of all stages in 1977. In 71% of the cases no or no sufficient postoperative control had been performed in the patients' own area. At the follow-up investigations 11 recurrences in the anastomosis, 10 of which were operable, 20 distant metastases, 1 simultaneous second carcinoma, 15 adenomas, partially with numerous atypical cells, 1 polyposis coli and 23 nonspecific granulomas of the anastomosis were detected. The Haemoccult test was positive in 3 of the 11 anastomotic recurrences. Only in cases of distant metastases were values of carcinoembryonic antigen clearly increased (greater than 5 ng/ml). These findings underline the necessity of intensifying the regular follow-up investigation in colo-rectal carcinoma.