Pulmonary function in 25 patients with intrathoracic sarcoidosis was studied by three different methods: clinical, as related to the presence or absence of dispnea; response to corticoid treatment, and roentgenologic stage. A total of 60 examination were made on the 25 patients. Each examination included: pulmonary volume (vital capacity and RV/CT coefficient), ventilatory mechanics (elastance, resistance, critical flow, and specific conductance), and gas exchange (DCO/VA and (A-a) O2). The following results were obtained from statistical evaluation of the mean values compared with normal values: 1) patients with dyspnea showed a greater pulmonary elastance and (A-a) O2 than normal; 2) treatment with corticoids only produces an improvement in the diffusion capacity in respect to the total volume (DCO/VT); 3) examinations corresponding to the three different roentgenologic stages varied only in pulmonary volume and only when stage III was compared with stages I and II; 4) the terminal stage of the disease is physiologically similar to the typical pattern of emphysema.