We report a case of cytomegalovirus(CMV) pneumonitis in a 21-year-old woman with systemic lupus erythematosus(SLE). She was diagnosed 3 years ago with lupus nephropathy and was on immunosuppressive therapy with prednisolone and cyclophosphamide. She developed dyspnea with fever and hypoxemia. Chest X-ray, and HRCT showed interstitial pneumonitis. We performed open lung biopsy. The diagnosis of CMV pneumonitis was made by the virus culture and immunohistochemical staining for CMV in lung tissue. Despite the admini stration of ganciclovir and high dose immunoglobulin therapy and assistance of mechanical ventilator, the patient died.