Diffuse alveolar hemorrhage is a bleeding originating from the pulmonary acinus. Number of causes are possible, that can be divided in immune and non immune causes. Immune mediated diffuse alveolar hemorrhages are mainly due to small vessels vasculitis (Wegener granulomatosis, microscopic polyangiitis), systemic lupus erythematosus and antiglomerular basement membrane antibody disease. Early immunosuppressive treatment is required, mostly with pulse methylprednisolone and cyclophosphamide. Plasmapheresis are added in antiglomerular basement membrane antibody disease and refractory systemic lupus erythematosus. Non immune mediated diffuse alveolar hemorrhages are mainly due to cardiac failure, severe dyscrasia and idiopathic diffuse alveolar hemorrhage. Barotrauma, cancer microangiopathy, toxic or drug-induced diffuse alveolar hemorrhage are other rare causes. Whatever is the cause, diffuse alveolar hemorrhage is an emergency associated with an intrahospital mortality rate of approximately 20 percent.