Bronchiolitis obliterans organizing pneumonia (BOOP) is increasingly recognized in "Jordanovac" Clinical hospital for lung diseases. The characteristic pathohistologic finding is the granulated tissue plugs within the lumen of small airways which extend into the alveolar ducts and alveoli. Numerous conditions and diseases show such histologic picture but the clinician by means of clinical, radiologic and laboratory findings establishes the final diagnosis. By eliminating the known causes and conditions of this syndrome the diagnosis of idiopathic BOOP is established. Idiopathic BOOP is unequivocal clinicopathologic entity which is in typical cases recognized as a pulmonary infiltrate accompanied by febrile illness of a few weeks' duration that is not responsive to a typical course of antibiotics. Corticosteroid therapy causes the complete disappearance of pulmonary infiltrates in 65% to 85% of cases but relapses are common. The therapy of secondary BOOP is less efficient. The aim of this review is to acquaint the readers with the BOOP so it could be incorporated in the differential diagnosis of febrile noninfective diseases that resemble pneumonia.