210 patients harbouring an intracranial tumour were tested for CEA plasma levels. It could be shown that this investigation was neither a useful screening test for detecting brain neoplasms nor suitable for follow-up on operated brain tumours. However, with the CEA plasma investigation an additional preoperative test is available for distinguishing between primary and secondary brain tumours. The positive evidence is only 29%, but in case of a CEA plasma value above 5.0 ng/ml a metastasis is indicated with a probability of 91%.