We investigated cellular composition of bronchoalveolar lavage fluid and changes in pulmonary function tests in patients with histopathologically proven sarcoidosis. We analyzed BAL, lung volumes, lung compliance, and diffusing capacity in 33 nonsmoking patients (18 males, 15 females, age 22-60 years, mean 40 years). In 39% of the patients we observed decreased static compliance and in 18% of patients reduction in diffusing capacity. The total cell count, percentage of lymphocytes and CD4/CD8 ratio and pulmonary function parameters in I, II and III radiological stages of sarcoidosis were similar. We found a moderate negative correlation between the carbon monoxide diffusing capacity (DLco% of pred.) and CD4/CD8 ratio (r = -0.40, p < 0.05). No correlation was observed between other pulmonary function indices and total cell count in BAL, percentage of lymphocytes and CD4/CD8 ratio. Our results suggest, that reduction in diffusing capacity may reflect an insensitivity of alveolitis, but correlation is moderate and it usefulness for making therapeutic decision is not clear.