The term pulmonary-renal syndrome refers to the combination of diffuse alveolar haemorrhage and rapidly progressive glomerulonephritis. It is usually a manifestation of an autoimmune systemic disease, Goodpasture’s syndrome included. A variety of mechanisms such as anti-glomerular membrane antibodies, antineutrophil cytoplasmic antibodies, immunocomplexes, thrombotic microangiopathy are implicated in the pathogenesis of this syndrome. The underlying pulmonary histologic lesion is small vessel vasculitis characterized by an inflammatory destructive process involving arterioles, venules and frequently alveolar capillaries (necrotic pulmonary capillaritis). Haemoptysis is the most frequent clinical manifestation of diffuse alveolar haemorrhage. However, 30-35% of patients may not present the symptom. In this case the following suggest the diagnosis: 1) a chest roentgenogram revealing multiple coalescent alveolar shadows, 2) acute decrease of hematocrit, 3) haemorrhagic bronchoalveolar lavage, and 4) increased Kco. In patients with evidence of diffuse alveolar haemorrhage and renal involvement, kidney biopsy should be considered to identify the underlying cause and help direct the therapy. Pulmonary-renal syndrome is related to significant morbidity and mortality and is often complicated by life threatening side effects attributed to immunosuppressive treatment. Its fulminant course requires early diagnosis and initiation of therapy including corticosteroids in high doses and cytotoxic agents. In some cases plasmapheresis is indicated. The role of new agents such as anti-TNFa is under investigation. Pneumon 2006, 19(3):168-179.