BACKGROUND Carcinoembryonic antigen (CEA) is an oncofetal glycoprotein involved in cell recognition and adhesion. Serum CEA has been extensively studied as a potential chemical marker for malignancy, most notably in patients with colon carcinoma. Serum CEA measurements have not been reported for patients with salivary gland carcinomas. METHODS Serum CEA was measured in a case study using enzyme immunoassay with monoclonal antibody specific for CEA. Tissue was examined with standard histologic and immunohistologic methods. RESULTS A patient was initially seen with adenoid cystic carcinoma (ACC) of the trachea and had a markedly elevated serum CEA level which declined after surgical resection. The serum CEA level became elevated again when the patient developed abdominal metastases and then declined after debulking of the tumor. Immunohistochemical study of the tumor was positive for CEA. CONCLUSIONS The measurement of serum CEA levels may play a role in the management of patients with ACC. Clinical investigation utilizing monoclonal antibodies against CEA, for imaging and for the delivery of chemotherapy and radiotherapy may be worthwhile.