Gold lung is a hypersensitivity pneumonitis to gold-containing compounds. It can be distinguished from rheumatoid lung by its subacute or acute onset, diffuse interstitial and/or alveolar filling pattern on chest roentgenogram, presence of lymphocytes on BAL with an inverse helper/suppressor ratio, and response to withdrawal of gold and/or corticosteroid therapy. Other in vitro assays of gold hypersensitivity using peripheral blood lymphocytes are only sporadically positive and, therefore, of limited value in making the diagnosis. Physicians prescribing organic gold compounds should elicit pulmonary complaints throughout the duration of therapy. When patients receiving gold therapy present with signs and symptoms consistent with an acute or subacute hypersensitivity pneumonitis, the gold therapy should be withheld and a diagnostic workup initiated.