Inhalation of metal dust or fume can cause granulomatous lung disease that mimics sarcoidosis. Particular metals that possess antigenic properties which promote granuloma formation include aluminum, barium, beryllium, cobalt, copper, gold, rare earths (lanthanides), titanium, and zirconium. The occupational and environmental exposure history holds the key to linking such metals with seemingly idiopathic disease. We propose clinicians use a systematic approach to investigating the occupational and environmental history and immunologic responses of patients with sarcoidosis, in order to discriminate metal-induced granulomatosis from sarcoidosis.