A patient with bronchiolitis obliterans organizing pneumonia (BOOP) associated with acute Mycoplasma pneumoniae infection is described. Although mycoplasmas have occasionally been associated with bronchiolitis obliterans, to the best of our knowledge, this is the first well-documented case of BOOP associated with M. pneumoniae infection. The diagnosis of BOOP was made by open-lung biopsy after fiberoptic transbronchial biopsy proved nondiagnostic. Corticosteroid therapy was administered and a dramatic improvement was observed; the patient remained without complaints during a 3-year follow-up period.