Background: Gastroesophageal reflux (GER) is the presence of gastric contents proximal to the stomach. Pathologic consequences secondary to GER are termed gastroesophageal reflux disease (GERD). Objectives: The purpose of this study was to determine the prevalence of GER and GERD in premature calves by endoscopic examination. Animals: Ten healthy and 51 premature calves were included in the study. All premature calves also had respiratory distress syndrome. Methods: Esophagoscopy of premature calves was conducted by fiber optic endoscopy. Abnormalities such as increased saliva, hyperemia, hemorrhage, petechiae, presence of abomasal content in the esophagus, and relaxation of the lower esophageal sphincter (LES) were evaluated by endoscopy. Results: The prevalence of GERD and GER in the premature calves was 55 and 67%, respectively. Hyperemia and hyperemia with hemorrhage or petechiation of the esophageal mucosa were determined by endoscopic examination. Hyperemia was commonly observed in the distal esophageal mucosa, although a few hyperemic areas also were observed in other portions of the esophagus. In addition to these abnormalities, LES relaxation, abomasal fluid in the distal esophagus, abomasal content in the esophagus, and increased saliva also were observed in premature calves with GER. Conclusions: The prevalence of both GER (67%) and GERD (55%) in premature calves was high in the study. Endoscopy provides a practical, rapid, noninvasive, and reasonably accurate method for determining the presence of GER and GERD in premature calves. © 2012 by the American College of Veterinary Internal Medicine.