Sarcoidosis is a systemic disease of unknown etiology, characterized by formation of noncaseating granulomas in the lung, lymph nodes, and multiple other organs. Patients are often asymptomatic, with bilateral hilar lymphadenopathy or pulmonary reticulonodular infiltrates on chest radiograph. Lungs are involved in more than 90% of patients. Most patients demonstrate elevated serum angiotensin-converting enzyme (ACE), increased uptake of gallium, and skin anergy. Sarcoidosis is a diagnosis of exclusion; infectious causes for pulmonary granulomas should always be excluded, not only by special stains on the biopsy specimen but also by cultures.