During a 3 year period, 101 patients were consecutively diagnosed as having sarcoidosis. During the 3 year follow-up 9 patients died, 6 of them directly or indirectly due to their sarcoidosis. In 78 patients bronchoscopy and spirometry were performed at the primary investigation, and after 3 years a new spirometry was performed. A positive bronchial mucosal biopsy, bronchial sarcoidosis, was found in 31 (40%) of the 78 patients. Mean values of vital capacity, total lung capacity and forced expiratory volume in one second were normal in both patients with bronchial sarcoidosis and those without. Abnormal spirometry was found in 16 (21%) patients at the initial examination and in 11 (14%) at the follow-up. There were 10 (32%) patients with and 6 (13%) without bronchial sarcoidosis who had an abnormal spirometry. At follow-up a normalized lung function was found in 8 (50%) of the 16 patients with abnormal spirometry. Only 3 (4.8%) patients with initially normal lung function had abnormal lung function at follow-up. Our findings indicate a very little risk of developing abnormal lung function if there are normal findings at the primary investigation. Corticosteroids seem to have some effect, especially in patients with endobronchial sarcoidosis.