OBJECTIVE. The aim of our study was to assess the effect of IV erythromycin on gastric emptying and subsequent small-bowel filling using three-dimensional (3D) MR imaging in both healthy subjects and patients with functional dyspepsia. SUBJECTS AND METHODS. Six healthy volunteers and six patients with symptoms of functional dyspepsia ingested 10 mL of gadopentetate dimeglumine mixed into 500 mL of a liquid nutrient. On two separate days, gastric emptying was determined using 3D volume measurements that were obtained every 5 min for as long as 25 min on 3D T1-weighted gradient-echo MR imaging with and without the use of IV erythromycin. Gastric volumes and filling of the small bowel were quantified on the 3D data sets using semiautomatic software. RESULTS. Delineation of the bright gastric lumen proved easy. After 25 min, a significant decrease in gastric volumes could be seen in examinations performed with and without erythromycin. In healthy volunteers, gastric volumes decreased significantly more after the administration of erythromycin. In three patients with functional dyspepsia, MR imaging revealed reduced rates of gastric emptying. The administration of erythromycin resulted in a significantly faster rate of gastric emptying in two of those three patients. CONCLUSION. Three-dimensional MR imaging is a feasible method of assessing gastric volumes and diagnosing delayed gastric emptying. In patients with reduced rates of gastric emptying, 3D MR imaging may be an appropriate tool with which to monitor therapeutic approaches, such as the use of prokinetic agents like erythromycin.