Pulmonary sarcoidosis was studied with respect to lung mechanical properties and to the influence of these on lung volumes. Sixty-six patients, with histological support for the diagnosis of sarcoidosis, and radiological signs of pulmonary involvement, i.e., stage II or III, were studied. The static pressure/volume (P/V) curves showed that the static elastic recoil pressure (PelL) tended to be increased at a given percentage of predicted total lung capacity (TLC). Reduction of static lung compliance (CstL) was a typical finding. At maximal inspiration PelL was abnormally low in 20 subjects, including in the main those with recent onset of the disease and older patients. The possibility of a greater inflammatory activity at the site of mechanical receptors in the lungs and airways of these patients is proposed. Pulmonary resistance, measured at a given PelL, was usually increased signifying bronchial involvement. TLC, residual volume (RV) and functional residual capacity (FRC) were lower in current smokers and ex-smokers than in lifelong nonsmokers. This may be due to synergistic effects of the inflammatory processes caused by smoking and sarcoidosis. A reduced vital capacity (VC) mainly reflected a low CstL but also obstruction with increased RV. Forced expiratory volume in one second (FEV1) reflected lung stiffness and obstruction equally. Lung mechanics revealed functional abnormalities which were not obvious from the standard tests, particularly in patients with respiratory symptoms.