A 74 year old female presented with fever, associated with papules and plaque in her upper and lower extremities. Exams revealed blood leukocytosis and a positive urine culture. Antibiotic therapy was initiated with no clinical response. After 1 week, chest X-ray showed right upper lobe alveolar infiltrate. A skin biopsy of the lesion showed infiltration by neutrophils, consistent with Sweet's Syndrome. Patient's condition progressively worsened, requiring oxygentherapy. Bronchoscopy and bronchoalveolar lavage were normal, transbronchial biopsies suggested lung involvement of Sweet 's syndrome. Antibiotic therapy was stopped. Corticosteroid were started. Therapy resulted in rapid clinical and radiological improvement.