The awareness that sarcoidosis can involve intrathoracic lymph nodes and lung parenchyma in sequential fashion evolved during the first half of this century. This awareness resulted in a roentgenographic staging system that has relevance to the course and prognosis, pulmonary function changes, and the symptom of dyspnea. The following definition or roentgenographic staging is proposed as the simplest, most reproducible system based solely on the roentgenographic appearance, avoiding histopathologic and pathophysiologic inferences. Stage I: bilateral hilar lymphadenopathy; stage II: bilateral hilar lymphadenopathy plus parenchymal infiltration; and stage III: parenchymal infiltration without bilateral hilar lymphadenopathy. The early data concerning bronchoalveolar lavage, determination of serum angiotensin-converting enzyme, and gallium 67 citrate scanning appear to have no clear relationships to staging, suggesting that staging continues to have unique value to the clinician in the classification of sarcoidosis and in the delineation of its clinical course and prognosis.