A 16-year-old male developed fever and productive cough of 2 months' duration. Extensive search for an infectious process was negative. After appearance of knee joint effusion, a transbronchial biopsy through a fiberoptic bronchoscope revealed histological findings consistent with sarcoidosis. The patient recovered after a course of prednisone therapy. The atypical presentation of this systemic disease caused considerable delay in diagnosis and initiation of treatment.