This review critically evaluates the gastroduodenal factors that may play a clinically relevant role in the pathogenesis of reflux esophagitis. The gastroesophageal pressure gradient is of obvious importance, but the role of gastric contraction/relaxation is poorly understood. The intragastric volume, as well as the factors that influence it, could theoretically play a role in gastroesophageal reflux (GER). For example, suppression of gastric emptying and gastric motility would be expected to increase GER, and treatment with gastrokinetic agents appears to provide symptomatic improvement. However, only a fraction of patients with GER have delayed gastric emptying, and there is no correlation between either subjective epigastric fullness or esophagitis on one hand and gastric emptying on the other hand. Gastric acid and pepsin, and possibly the hypersecretion of acid, play a pivotal role in reflux esophagitis, as demonstrated by the efficacy of the treatment with histamine H2 antagonists and antacids. Other important factors in experimental esophagitis are duodenogastric reflux, the presence of bile acids in the gastric contents, as well as trypsin if the pH is alkaline. It is suggested that these important findings may lead to novel therapeutic approaches of reflux esophagitis.