It has been suggested that shifts in gastric and esophageal pH can be used to estimate the reflux of injurious alkaline material, particularly bile, into the esophagus. We sought to evaluate the contribution of swallowed saliva to alkalinization of both the stomach and esophagus in 10 normal volunteers, by performing combined gastric and esophageal pH monitoring before, during, and after salivary stimulation. The intraesophageal pH universally increased during salivary stimulation, whereas the intragastric pH was noted to increase in six of 10 subjects. In four of these six, the pattern of simultaneous increases in esophageal and gastric pH mimicked and could be mistaken for episodes of "alkaline reflux." We conclude that the diagnosis of reflux of duodenal contents into the esophagus by pH monitoring may be compromised by false-positive results related to swallowed saliva.