Acute lung injury (ALI) is the clinical syndrome associated with histopathologic diffuse alveolar damage. It is a common cause of acute respiratory symptoms and admission to the intensive care unit. Diagnosis of ALI is typically based on clinical and radiographic criteria; however, because these criteria can be nonspecific, diagnostic uncertainty is common. A multidisciplinary approach that synthesizes clinical, imaging, and pathologic data can ensure an accurate diagnosis. Radiologists must be aware of the radiographic and computed tomographic findings of ALI and its mimics. This article discusses the multidisciplinary diagnosis of ALI from the perspective of the imager.