A 42-year-old renal transplant recipient was admitted with fever, anorexia, malaise, nonproductive cough, and dyspnea of 1-week duration. Multiple cultures of blood, sputum, and urine were negative. The possibility of bronchiolitis obliterans with organizing pneumonia (BOOP) was considered when pulmonary infiltrate did not respond to conventional antibiotic therapy. High-resolution computed tomography of the chest revealed patchy air-space consolidation and ground-glass opacities, predominantly located in the periphery of the lungs. Cultures and stains of bronchoalveolar lavage specimen and bronchoscopic biopsy of lung tissue were negative for organisms such as Pneumocystis (carinii) jiroveci, bacteria, Mycobacterium tuberculosis, cytomegalovirus, fungi, and atypical germs, and showed evidence of BOOP. The patient recovered completely after treatment with steroids.