Idiopathic pulmonary hemosiderosis (IPH) is a rare disorder characterised by intermittent, diffuse alveolar hemorrhage (DAH). Although an inflammatory pulmonary capillaritis can be evidenced in most patients with DAH, IPH is a distinct entity in which pulmonary inflammatory alterations are lacking. Most cases occur in children, although the disease has been exceptionally reported in adults too. Here, we, describe a case of IPH in a 30-year-old woman who was admitted to our hospital because of recurrent episodes of hemoptysis since the age of 21. IPH was diagnosed on the basis of: 1) an open lung biopsy showing focal alveolar edema and hemorrhage without parenchymal inflammatory alterations, 2) a bronchoalveolar lavage showing hemosiderin-laden macrophages, and 3) exclusion of infectious or immunologic causes of hemoptysis. Prednisone administration could control the disease, but every attempt to lower the dose to less than 25 mg per day was followed by recurrence of hemoptysis. Then, azathioprine was started, and after three months prednisone was gradually tapered to the dose of 10 mg per day, without any relapse of the disease. These findings indicate that azathioprine, in combination with prednisone, may be an effective therapy for IPH and suggest that an immunologic mechanism could be involved in the pulmonary capillary damage underlying alveolar bleeding.