Acute or subactute pulmonary damage can be either idiopathic or resulting from a known cause. The most common histologic types are diffuse acute alveolar damage (DAD) and organizing pneumonia (OP). Various kinds of infection, pulmonary drug reactions or acute exacerbations of interstitial lung diseases may cause DAD, often requiring intensive care. High-resolution computed tomography (HRTT) of the lungs is the most important diagnostic examination. Surgical lung biopsy is performed for few patients.