The effects of theophylline on lower esophageal sphincter pressure (LESP) were studied on four normal volunteers and six asthmatics with symptoms of gastroesophageal reflux (GER). Manometric evaluations of LESP were obtained before and after an intravenous dose of aminophylline. All subjects had therapeutic theophylline levels at the time of the second measurement of LESP and a significant decrease in LESP occurred in normal and asthmatic volunteers.