A previously healthy young man presented with acute respiratory distress and diffuse bilateral infiltrates on chest radiograph. Eosinophilic pneumonia was diagnosed by bronchoalveolar lavage and confirmed by transbronchial lung biopsy. There was no evidence of an infectious etiology, and the patient rapidly improved with corticosteroid therapy. Most cases of eosinophilic pneumonia reported previously have followed a chronic course. The case presented here was acute in onset, suggesting a hypersensitivity reaction. High levels of bronchoalveolar lavage eosinophils indicate the diagnosis but not the etiology of eosinophilic pneumonia.