One hundred and seven patients with sarcoidosis attended for pulmonary function testing within 2 weeks of diagnosis. In four Stage 0, 42 Stage I, 32 Stage II, 26 Stage III and three Stage IV patients physiological abnormalities increased with increasing stage. The commonest abnormality, airflow limitation, occurred in 61 patients; a low transfer factor occurred in 29; a restrictive defect, the least common abnormality, occurred in seven. Fifty-nine patients and 30 of those with evidence of airways obstruction never smoked. None of the 52 patients with airflow limitation tested after bronchodilator inhalation demonstrated significant reversibility. All patients with obstruction had evidence of small airways narrowing. The majority had an FEV1/FVC ratio below 75%. Fourteen patients also had a low peak expiratory flow indicative of large airway narrowing. Airflow limitation occurs in all stages of sarcoidosis and should always be looked for in patients with sarcoidosis who have respiratory symptoms.