Background: Carcinoembryonic antigen (CEA) as a marker in the follow-up after curative resection of colorectal carcinoma (CRC) is often omitted from follow-up despite guideline recommendations. One reason is the assumption that when a normal CEA value exists before curative resection of CRC, it will neither rise during follow-up. This study investigates this relationship. Method: Data were derived from a study initiated to evaluate treatment regimes for rectal carcinoma (Dutch TME trial, n = 1861) from which 954 were eligible for analysis. Recurrent disease occurred in 272 of these patients (29.5%). The pre-operative CEA value was compared to CEA values during follow-up, using threshold values of 2.5 and 5.0 ng/ml. Results: Normal pre-operative CEA values were present in 63% (CEA < 5.0) and 39% (CEA < 2.5) of patients with recurrent disease. Patients with a normal pre-operative CEA and recurrent disease had elevated CEA values during follow-up in 41% (CEA < 5.0), 50% (CEA < 2.5) and in 60% with both threshold values when the last measurement was done within 3 months before recurrent disease was diagnosed. Conclusion: A normal pre-operative CEA is common in patients with rectal carcinoma. CEA does rise due to recurrent disease in at least 50% of patients with normal pre-operative values. Serial post-operative CEA testing cannot be discarded based on a normal pre-operative serum CEA.@en