Dynamic computed tomography illustrates the real-time spatial distribution of lung aeration during mechanical ventilation in experimental lung injury. Lung injury was induced by oleic acid infusion (see video; Supplemental Digital Content 2, https://links.lww.com/ALN/B849). Pressure-controlled ventilation (driving pressure 20 cm H₂O, rate 32 min^–1, inspired O₂ 40%) with lower positive end-expiratory pressure (PEEP; 5 cm H₂O; A) or higher PEEP (10 cm H₂O; B) was used. [i] End-inspiratory computed tomography (transverse, sagittal, coronal planes). [ii] Minimum intensity projection voxels. [iii] Time-varying fractions of lung at normally aerated, poorly aerated, and nonaerated levels are illustrated. The following features are observed. Hyperaerated tissue (not visible) accounted for less than 1% of lung voxels at either level of PEEP. The intratidal changes in normal, poorly, and nonaerated fraction were 15, 10, and 5%, respectively, at the two PEEP levels. However, there was a nearly twofold increase in nonaerated tissue at the lower PEEP, as well as noticeable flooding of large bronchi in the right lung, and arterial hemoglobin O₂ saturation was 92 versus 63% with PEEP 10 versus 5 cm H₂O. Normal, poor, and nonaeration is considered: –900 to –500, –500 to –100, and above –100 HU, respectively.