PURPOSE To determine the accuracy of magnetic resonance imaging (MRI) volume scans: 1) to measure known meal volumes in vitro, and 2) to compare volume changes in response to a meal measured with the barostat with those measured with MRI in vivo. MATERIALS AND METHODS Polyethylene bags were filled with known volumes and MRI volume scans were performed to determine the accuracy of the volume measurements. Barostat measurements and MRI volume scans were performed simultaneously in 14 healthy subjects before and up to 90 minutes after ingestion of a liquid meal. RESULTS In vitro MRI-determined volumes showed an excellent linear relationship (r = 0.995, P < 0.001) with actual meal volumes. Although fasting gastric volume, postprandial gastric volume, and relaxation volume measured with MRI were significantly larger compared to volumes measured with the barostat, volumes determined with both techniques showed excellent correlation. CONCLUSION Volumes in the range of postprandial meal volumes are accurately measured with MRI. MRI is a noninvasive technique to measure stomach volumes and volume changes in response to a meal. Volume changes in response to a meal measured with MRI correlate perfectly with those measured with the barostat device.