Diffuse alveolar hemorrhage (DAH) is often a catastrophic clinical syndrome causing respiratory failure. Recognition of DAH often requires BAL as symptoms are nonspecific, hemoptysis is absent in up to one-third of patients, and radiographic imaging is also nonspecific and similar to other acute alveolar filling processes. Once the diagnosis is established, the underlying cause must be established in order to initiate treatment. This review discusses the diagnosis of the underlying histologies and the clinical entities that are responsible for DAH as well as treatment options.