The lung is frequently involved in systemic disease either as the primary site of the lesion or as an extension of processes which are occurring in other organs. Most of the pulmonary changes associated with these diseases are centered in the parenchyma; however, a few affect the bronchial tissues and the adjacent parenchyma which are reached by bronchial biopsy. Principal among these is sarcoidosis which has been mentioned in Chapter 6 but is discussed further here. The remaining examples are rather rare and the patient’s underlying disease is generally known to the clinician at the time of bronchoscopy. More often than not the reason for the bronchoscopy in these cases is for diagnosis of other suspected secondary diseases and the expression of the systemic disease is a curiosity. Nevertheless, occasional biopsy material may suggest, to the observant pathologist, systemic disease previously unrecognized clinically.