['To assess the influence of mediastinal lymphadenectomy on postoperative concentration of interleukin 6 (IL-6) and interleukin 1 receptor antagonist (IL-1 ra) in serum, sputum, and pleural fluid, in patients operated upon due to lung cancer and benign pulmonary diseases.', 'Thirty-three patients undergoing uncomplicated resections, including 23 with lung cancer and 10 with benign diseases, were analyzed. In patients with right lung cancer we performed a systematic lymphadenectomy, while in patients with left lung cancer systematic sampling was performed. Serum IL-6 and IL-1 ra concentration was measured before and after surgery, and on postoperative days 1, 3, and 7, as well as in sputum at the end of surgery and in pleural fluid on postoperative day 1, by ELISA test.', 'In 23 patients with cancer, 19.0+/-11.43 mediastinal lymph nodes were removed (in 11 patients with right lung cancer 27.6+/-7.6 and in 12 patients with left lung cancer 11.1+/-8.1). No differences were found in serum and sputum concentration of IL-6 and IL-1 ra between patients after right and left thoracotomy due to cancer and between patients with cancer and patients with benign diseases. Patients with cancer had a lower concentration of IL-1 ra in pleural fluid (median 16950, range 16050-45470.05 pg/ml) than patients with benign diseases (76665.6 pg/ml (range 53618-89617.9); p=0.0008). In 23 cancer patients a negative correlation between concentration of cytokines in pleural fluid and a number of mediastinal lymph nodes resected was observed (Spearman correlation coefficient for IL-6: r=-0.44, p=0.04; for IL-1 ra: r=-0.57, p=0.01). Such correlation was not observed for a number of positive N2 lymph nodes.'] Does systematic mediastinal lymphadenectomy increase postoperative immune response after major lung resections?