We presented a case of pulmonary Rhizops microsporus var. rhizopodiformis infection which developed abruptly during treatment of bronchial asthma by systemic corticosteroids. The patient, an 85 year-old-woman, was given systemic steroid therapy for 15 days. She suddenly became febrile two days after the therapy and was coughing up yellow sputum. Chest X-ray film showed multiple nodules with cavities which became worsened rapidly. A specimen of sputum culture gave a growth of Mucoraceae, which was identified to be Rhizopus microsporus var. rhizopodiformis. She was given amphotericin B and miconazole was added on the basis of MIC value of the strain. Although she improved initially, her clinical course showed neutropenia, pseudomembranous enterocolitis, malnutrition, and then died after about six months. Because the diagnosis of pulmonary mucormycosis is difficult and prognosis is poor, further studies for investigating clinical features would be necessary.