This report describes an industrial accident in which 5 previously healthy persons were acutely exposed to very high concentrations of sulfur dioxide. Of these 5 subjects, the 2 with the highest exposure died immediately; histologic examination of the lungs revealed extensive sloughing of the mucosa of large and small airways along with hemorrhagic alveolar edema. The 3 survivors were evaluated with pulmonary function tests performed at regular intervals. One subject subsequently developed symptomatic severe airway obstruction unresponsive to bronchodilators; another subject developed asymptomatic mild obstructive and restrictive disease, and the third subject continued to be asymptomatic with normal pulmonary function tests. This report severe to document the histologic features of fatal exposure to sulfur dioxide and stresses the need to follow parameters of pulmonary function in the nonfatal cases.