The most common type of esophageal dysfunction associated with chest pain is gastroesophageal reflux, which may be induced by exercise. The effect of exercise on esophageal function has mainly been investigated in normal subjects or trained athletes. Few studies have investigated exercise and esophageal motility disorders. One hundred and thirty-five patients underwent ambulatory esophageal manometry and pH monitoring, before, during and immediately after moderate exercise. Patients were divided into four groups: Normal, nutcracker, diffuse spasm and gastroesophageal reflux disease (GERD). Ambulatory manometry and pH were monitored while exercising on a treadmill during which standardized boluses of water were administered. Nutcracker and diffuse spasm patients demonstrated a significant fall in esophageal wave amplitude during exercise compared to controls, which returned rapidly to pre exercise values after resting. There was no evidence of acid reflux in the non-reflux groups during exercise. Reflux was noted in 13 patients with GERD during exercise, none of whom had evidence of reflux at the onset of exercise. When these patients were classified by reflux type, the majority, 11 patients, were found to come from the combined or supine reflux group. Esophageal amplitude in nutcracker esophagus does not increase during moderate exercise. Moderate exercise provokes reflux in GERD patients with combined or supine reflux.