Pulmonary involvement in Sweet's syndrome (SS) is rare. We report a case of SS with severe respiratory involvement responding to corticosteroid therapy. A 82-year-old man presented fever of 39 degrees C associated with cough and dyspnea, and crackles in the left lung. The infection work-up was negative. Chest X-ray showed cardiomegaly and left lower lobe pulmonary infiltrates. Pulmonary signs did not improve on treatment with antibiotics, and after 1 week maculopapular lesions appeared, localized on the knees, the periombilical area and the back. The antibiotics were changed without improvement. A skin biopsy revealed infiltration by neutrophilic granulocytes and marked edema in the dermis, consistent with SS. The patient's condition progressively worsened, requiring high oxygenotherapy, and he was transferred to an intensive care unit. Chest X-ray revealed an important alveolar and interstitial syndrome. Bronchoalveolar lavage found 170 leukocytes with 30% neutrophils (N < 5%), 7% lymphocytes and 63% macrophages. A search for bacteria, viruses or parasites in bronchoalveolar lavage was negative. The patient was treated with antibiotics, a high dose of furosemide and steroids for 4 days. Because the patient improved dramatically within 5 days, with a negative infection work-up and a dramatic decrease of C-reactive protein, the antibiotics were stopped. Steroids were secondarily tapered very slowly. A chest computed tomography (CT) scan showed a substantial improvement of pulmonary lesions. We also review the 22 cases of pulmonary involvement of SS reported in the literature.