A 65-year-old woman with endobronchial carcinoma had torsion of the left upper lobe. A posteroanterior chest radiograph showed apparent atelectasis in the left upper lobe, but the lateral view disclosed an inappropriate posterior displacement of the collapsed lobe. The vasculature of the affected area showed an unusual curvature. Review of 21 examples of lung torsion disclosed no characteristic age, sex, or affected lobe. The most common associations were with previous surgery (n = 10) or a history of trauma (n = 5). The most common radiographic findings are opacification of the affected lobe (n = 12), an abnormal vascular pattern (n = 6), and an abnormal location for the atelectatic lung (n = 5). Affected lobes often show hemorrhagic infarction or necrosis.