We have undertaken cellular and biochemical examination of bronchoalveolar lavage fluid from nonallergic patients with asthma to determine the nature and degree of inflammatory process in symptomatic asthma. Six patients with asthma (mean methacholine provocative concentration causing a 20% fall in FEV1 was 0.26 mg/ml) and six control subjects underwent fiberoptic bronchoscopy with bronchoalveolar wash. The patients with asthma shed a higher number of epithelial cells into lavage fluid than normal control subjects (p less than 0.05). Their lavage fluid also contained increased numbers of neutrophils (p less than 0.025), eosinophils (p less than 0.025), and basophilic cells (p less than 0.025), and increased proportion of activated T cells (p less than 0.05). The basophilic cells were mast cells, as indicated by positive labeling with the monoclonal antibody MCG35. Biochemical analysis of lavage fluid demonstrated exudation of protein molecules in airways of patients with asthma with increased contents of albumin (p less than 0.05) and fibronectin (p less than 0.05). In the lavage fluid of patients with asthma, there were also increased amounts of interleukin-1-beta (IL-1-beta) (p less than 0.025), interleukin-6 (IL-6) (p less than 0.025), and granulocyte-macrophage, colony-stimulating factor (GM-CSF) (p less than 0.05), as compared with lavage fluid of normal control subjects. Immunocytochemical evaluation of lavage cells demonstrated that IL-1-beta, IL-6, and GM-CSF were mostly produced by nonciliated epithelial cells and/or monocytes. IL-1, IL-6, and GM-CSF can prime granulocytes to respond to other stimuli and can promote T cell activation.(ABSTRACT TRUNCATED AT 250 WORDS)