&NA;In the past five years, routine CEA determinations have been carried out on all patients after curative operation for colorectal carcinoma. These patients also underwent a clinical follow‐up examination in the Oncology Outpatient Department. In 86 patients, recurrence of a tumor was confirmed. In 31 cases, a second‐look operation was carried out. The CEA determinations were retrospectively analyzed in these patients and correlated with the time the recurrence of the tumor was diagnosed. These results show that of 86 patients only 15 (17.4 per cent) had pathologic CEA values before clinical symptoms of tumor recurrence. In the patient group with local recurrence only 11 (23.9 per cent) of 46 patients had previously pathologically raised CEA values. Of 31 patients, 15 (48.4 per cent) underwent curative resection after the second‐look operation. At this time, 12 patients (38.7 per cent) still had normal CEA values, whereas only three patients (9.7 per cent) had pathologically raised CEA values. From these results, it was established that early diagnosis of tumor recurrence was very low. Therefore, one should not rely more on postoperative routine CEA determinations in the post‐operative monitoring of patients following curative operations for colorectal carcinoma than on regular comprehensive follow‐up examinations of these patients.