A method for outpatient 24-hr simultaneous recording of pH in the distal esophagus, fundus, and antrum was developed in order to detect acid, alkaline, alkalacid gastroesophageal reflux, and duodenogastric reflux and to study these phenomena in patients complaining of gastroesophageal reflux and dyspepsia related symptoms. Two hundred ninety-four studies were performed in 42 healthy volunteers and 237 patients. Three-probe ambulatory 24-hr esophagogastric pH monitoring applicability, tolerability, and capability to determine a relationship between symptoms which occurred during the tests, gastroesophageal reflux, and duodenogastric reflux episodes were assessed. Eighty-nine percent of the three-probe esophagogastric pH studies were easily performed. The examination was tolerated well by 86.1% of the patients and poorly by 13.9%. A temporal correlation between symptoms and pH activities was recognized in 61.3% when the esophageal tracing was considered (acid gastroesophageal reflux recording) and in 95.6% when the three pH traces were simultaneously interpreted. Alkalacid gastroesophageal reflux and duodenogastric reflux total percentage times were significantly higher in patients complaining of dyspeptic symptoms than in patients only affected by typical gastroesophageal symptoms. Three-probe 24-hr ambulatory esophagogastric pH monitoring is a simple, well-tolerated test that should be routinely adopted for the study of patients complaining of unclear upper gastrointestinal tract symptomatology.