Animal models play a critical role in the study of the acute respiratory distress syndrome (ARDS) and ventilator-induced lung injury (VILI). One limitation has been the lack of a suitable method for serial assessment of acute lung injury (ALI) in vivo. In this study, we demonstrate the sensitivity of magnetic resonance imaging (MRI) to assess ALI in real-time in rat models of VILI. Sprague-Dawley rats were untreated or treated with intratracheal lipopolysaccharide or PBS. After 48 hours, animals were mechanically ventilated for up to 15 hours to induce VILI. Free induction decay (FID)-projection images were made hourly. Image data were collected continuously for 30 minutes and divided into 13 phases of the ventilatory cycle to make cinematic images. Interleaved measurements of respiratory mechanics were performed using a Flexivent ventilator. The degree of lung infiltration was quantified in serial images throughout the progression or resolution of VILI. MRI detected VILI significantly earlier (3.8 ± 1.6 hours) than detection by altered lung mechanics (9.5 ± 3.9 hours; p=0.0156). Animals with VILI had a significant increase in the Index of Infiltration (p=0.0027), and early regional lung infiltrates detected by MRI correlated with edema and inflammatory lung injury on histopathology. We were also able to visualize and quantify regression of VILI in real-time upon institution of protective mechanical ventilation. MR lung imaging can be utilized to investigate mechanisms underlying the development and propagation of ALI, as well as to test the therapeutic effects of new treatments and ventilator strategies on the resolution of ALI.