Understanding local pulmonary immunoregulatory mechanism(s) in patients with carcinoma of the lung is an important step towards the development of innovative methods of treatment. Prostaglandin E2 plays an integral role in immunoregulation. Therefore, we evaluated PGE2 concentrations in BALF from 18 patients with bronchogenic carcinoma, compared to that from six patients with pulmonary diseases other than carcinoma and ten normal smokers of similar age. The level of PGE2 in patients with lung carcinoma (158.1 +/- 88.7 pg/ml) was significantly (p less than 0.001) higher than the other two groups (16.2 +/- 6.9 and 4.4 +/- 3.4 pg/ml). Levels of PGE2 also varied among patients with carcinoma of different cell types. Patients with SQCA had significantly (p less than 0.001) higher levels of PGE2 (242.7 +/- 29.4 pg/ml) than patients with ADCA or SCCA (82.3 +/- 27.9 and 66.3 +/- 15.2 pg/ml, respectively). Furthermore, there was a marked difference in PGE2 concentration between carcinomatous lung and clinically noninvolved lung in patients with SQCA and ADCA. Further study is warranted to determine the interactions between PGE2 and other cytokines (interleukin-1, IL-2, and tumor necrosis factor), as well as the activity of cytolytic lymphocytes (LAK cells) in the lungs of patients with bronchogenic carcinoma.