Bronchoalveolar lavage (BAL) leukocyte-secreted cytokines are considered to be important mediators of the inflammatory and allergic reactions in the lung. This study examines quantitative changes in the level of tumor necrosis factor-alpha (TNF alpha) and interferon-gamma (IFN gamma) production in BAL cell cultures derived from patients (n = 11) with bronchial asthma. The secretion of TNF alpha and IFN gamma was determined in intact (unstimulated) and phytohemagglutinin/phorbol myristate acetate (PHA + PMA)-stimulated BAL leukocyte cultures and compared with that in control cultures. In all patients studied, the background and PHA + PMA-induced secretion of TNF alpha and IFN gamma was significantly (p < 0.001) higher than that in parallel control cultures. In contrast to BAL cell preparations, the capacity of TNF alpha and IFN gamma secretion by patients' peripheral blood mononuclear cells (PBMC) did not differ from that of control subjects. High spontaneous release of TNF alpha and IFN gamma by patients' BAL leukocytes, but not PBMC, suggest that in the pathophysiology of bronchial asthma, these cytokines may act as local pathogenic agents in the lung.