The effect of BAL and fiberoptic bronchoscopy on gasometric and spirometric parameters was studied in 22 patients with sarcoidosis and 15 volunteers. In 12 patients with sarcoidosis during the repeated BAL procedure the effect of oxygen supplementation (by nasal prongs 3 L/min) was analysed. Significant decrease of oxygen pressure (PaO2) and vital capacity was seen in patients undergoing BAL and fiberoptic bronchoscopy. The administration of oxygen during the BAL procedure prevented the fall in oxygen pressured.