Bronchilolitis obliterans is a distinct pathologic entity, characterized by the accumulationof pigmented macrophages within respiratory bronchioles and adjacent to air spaces, and thickening of the peribronchial interstitium. It has been reported to be associated with viral infection, drug, toxic fume, bone marrow transplantation, and connective tissue disorders such as rheumatoid arthritis, The etiology of bronchiolitis obliterans in the postrenal transplantation state is not yet clear, although several possibilities such as drug toxicity, graft-versus-host disease or postinfectious condition have been postulated. We presented three patients who had bronchiolitis obliterans, as a complication following renal transplantation. Chest radiograph showed bilateral perihilar reticular infiltration or ground glass appearnces that progressed to either diffuse alveolar consolidations or solitary nodule, The main finding in each lung biopsy was the presence of macrophages within respira ory bronchioles as well as in the neighboring alveolar ducts and alveoli, Alveolar septa in these areas often showed nonspecific thickening by fibrosis. mild chronic inflammatory cell infiltrate, and hyperplasia of alveolar lining cells and type II pneumocytes.