Patients with sarcoidosis frequently complain of exercise intolerance but reports of the value of static tests of pulmonary function in predicting disability have been contradictory. We studied 32 patients with sarcoidosis and dyspnea, correlating x-ray stages, spirometry and lung volume measurements with graded exercise testing. Patients demonstrated a reduction in maximum workload (Wmax) when compared to an age matched group of 7 normal subjects (p < 0.05). While ventilation (VEmax) at Wmax was lower in patients, when adjusted for workload (V/E/watt) there was relative hyperventilation (p < 0.05). Exercise induced arterial desaturation (PaO2 decrease) was significantly related to resting DLCO% predicted (r = 0.74, p < 0.05). When patients were separated into subgroups of > < DLCO 55% predicted, the lower diffusing capacity group had a lower Wmax and greater fall in exercise PaO2. Chest radiograph staging and the vital capacity proved to be poor predictors of exercise capacity though maximum impairment was associated with advanced x-ray changes and greater decreases in vital capacity. In conclusion, the magnitude of functional impairment may vary widely from apparent histopathologic involvement as reflected by chest x-ray and lung volumes. Actual exercise testing is necessary to accurately characterize and quantitate the impairment in patients with sarcoidosis complaining of dyspnea.