Plasma levels of carcinoembryonic antigen (CEA) were determined in 82 lung cancer patients before surgery and during the clinical course of the disease. Results were compared to those obtained in normal controls and in patients with lung inflammatory diseases. Furthermore, relationships between plasma CEA levels and survival were carried out. While CEA levels were not useful to make differential diagnosis, in our study, we hypothized the possibility to use CEA in prognostic evaluations.