We studied cells and proteins in bronchoalveolar lavage fluid examined at the First Department of Internal Medicine of Shinshu University Hospital between 1990 and 1994. The samples came from 21 healthy subjects and from 216 patients with various diseases. Lymphocyte counts were abnormally high in patients with bronchiolitis obliterans organizing pneumonia. Sjögren's syndrome, sarcoidosis and hypersensitivity pneumonitis. Neutrophil counts were very high in the patients with diffuse panbronchiolitis and in those with high-altitude pulmonary edema, and eosinophil counts were high in those with eosinophilic pneumonia. The CD4:CD8 ratio was significantly higher in the patients with stage I sarcoidosis than in the healthy subjects. The total protein concentration and the albumin concentration were significantly higher in the patients with eosinophilic pneumonia and in those with high-altitude pulmonary edema than in the healthy subjects, and these findings suggest that in those two conditions the permeability of the pulmonary microvasculature was abnormally high.