Sarcoidosis is a systemic granulomatous disease with predominant manifestation in the lungs, often presenting as interstitial lung disease. Pulmonary function abnormalities in sarcoidosis include restriction of lung volumes, reduction in diffusing capacity of the lung for carbon monoxide (D(L,CO)), reduced static lung compliance (C(L,s)) and airway obstruction. The aim of the present study was to assess various lung function indices, including C(L,s) and D(L,CO), as markers of functional abnormality in sarcoidosis patients. Results from 830 consecutive patients referred for lung function tests with a diagnosis of sarcoidosis (223 in stage I, 486 in stage II and 121 in stage III) were retreospectively analysed. The mean ± sd age of the patients was 40 ± 11 yrs; 18% were active smokers and 24% were former smokers. Normal total lung capacity was found in 772 (93%) patients. Of these cases, 24.5% had a low C(L,s) and 21.5% had a low D(L,CO). At least one abnormality was observed in 39.3% of these patients, whereas, in restrictive patients, this figure was 88%. Airway obstruction was present in 11.7% of cases. Lung volumes usually remain within the normal range and measurement of either C(L,s) or D(L,CO) often reveal impaired lung function in sarcoidosis patients, even when their lung volumes are still in the normal range; these two measurements provide complementary information.