OBJECTIVE To detect the tumor marker carcinoembryonic antigen (CEA) in pleural lavage fluid taken during surgery from patients with pulmonary carcinoma without associated pleural effusion and assess its possible prognostic implications. METHODS A prospective, observational study was undertaken to include consecutive patients who underwent surgical treatment for lung carcinoma in which pleural lavage was performed prior to closure of the thoracic cavity (study group). The same techniques and measurements were used in patients undergoing thoracotomy for benign disease (control group). The preoperative blood level of CEA was also quantified. RESULTS In the study group, the median CEA levels in blood and pleural lavage fluid were 2.90 ng/mL and 0.40 ng/mL respectively; these figures are higher than those corresponding to the control group. A CEA level of 0.30 ng/mL in pleural lavage fluid was established as a cutoff point, based on the corresponding receiver operating characteristic curve, with a sensitivity of 68.4% and a specificity of 35.7%. A graph of survival in relation to this cutoff point revealed a statistically significant effect (P<.05). CONCLUSIONS It is possible to detect CEA in pleural lavage fluid from the thoracic cavity of patients with lung carcinoma. The values obtained are higher than those found in fluid from patients without neoplastic disease, and this parameter functions as an independent predictor of disease course.