The macrolide antibiotic erythromycin has recently been reported to exert profound prokinetic properties. The aim of the study was to investigate the effect of erythromycin on postprandial gastroesophageal reflux in patients with reflux esophagitis. METHODS In 16 patients with reflux esophagitis (according to Savary and Miller: grade I, n = 8; grade II, n = 4; grade III/IV, n = 4) two pH measurements, with and without erythromycin, were performed for three postprandial hours after lunch. Erythromycin was administered in a dose of 3.5 mg/kg intravenously just prior to lunch. RESULTS With erythromycin, the median fraction time esophageal pH < 4 was significantly decreased (7.6% versus 18.1%; P < 0.05). This decrease was the result of a diminished frequency of reflux episodes (19 vs 25; P < 0.05) and a shortening of the median reflux duration (0.7 min vs 1.1 min; P < 0.05). CONCLUSIONS Intravenous administration of erythromycin decreases postprandial gastroesophageal reflux in patients with reflux esophagitis.