Organising pneumonia is an inflammatory and fibroproliferative reaction of the lung, which gives rise to a clinico-pathological syndrome. It may occur without any detectable cause (cryptogenic organising pneumonia) or may be associated with various processes such as infections, drug toxicities, connective tissue disorders, etc. (secondary organising pneumonia). The clinical picture is usually subacute and includes fever, fatigue, weight loss, cough, dyspnea, crackles, and elevated inflammatory markers. At imaging, the most typical pattern consists of multiple subpleural consolidations. Bronchoalveolar lavage reveals a mixed alveolitis with lymphocytes and polymorphonuclear cells. Lung biopsy shows buds of loose connective tissue filling the lung alveoli. The diagnosis is made by combination of clinical, imaging and histopathological criteria. Most patients respond very well to corticosteroid therapy. Relapses are common but can usually be controlled with moderate doses of prednisone, and do not worsen the prognosis.