Two hundred and twenty patients with symptoms suggestive of pathologic gastroesophageal reflux were investigated to elucidate the ability of symptoms and endoscopic findings in establishing a diagnosis of reflux disease as measured by ambulatory 24-h pH-monitoring. Daily occurrence of heartburn or acid regurgitation had positive predictive values of 59% and 66%, respectively. pH-monitoring showed pathologic reflux in 75% of patients with esophageal mucosal erosions. Endoscopic erythema of the distal esophagus predicted reflux disease in only 53%. Symptom registration during ambulatory 24-h pH-monitoring showed that about half of the symptomatic events reported by patients with pathologic reflux occurred within 5 min of a reflux episode. The corresponding figure for patients with normal pH-monitoring was less than 20%. We conclude that it is difficult to establish a diagnosis of gastroesophageal reflux disease by patient history alone, that erythema at endoscopy correlates poorly with pathologic reflux, and that reflux disease may be present even with normal endoscopy findings.