Although intraluminal manometry and cineroentgenogaphy have provided much information about esophageal motor function, these examinations do not adequately record esophageal motion, particularly motion of the esophagus along its longitudinal axis. Labelling the esophageal wall, esophagogastric junction and diaphragmatic hiatus with implanted metal markers, however, permits direct observation and recording of esophageal movement. The propose study describes a plan of evaluating, in humans and in animals, esophageal motion associated with peristalsis, respiration and other physiologic events. Esophageal dynamics will be studied in individuals and animals wih normal esophageal function and in others with altered esophageal motor function caused by esophagitis, hiatal hernia, drugs, vagotomy and other conditions. In consenting human adults, the esophagus and diaphragmatic hiatus will be labeled with small metal markers at time of elective thoracic or abdominal surgery performed for other reasons. Esophagi of cats, opossums and monkeys will be laveled by a technique shown not to cause important changes in esophageal motility or histology. A major aim of the study is to characterize the mechanisms associated with lower esophageal sphincter (LES) opening and the LES antireflux mechanism. Such information will permit better design of surgical hiatal hernia repair or valve producing procedures to prevent gastroesophageal reflux. Additional goals include evaluation and improvement of the systems used for measuring esophageal pressure, improvement and compariosn of the x-ray and manometric exams of esophageal motor function and utilization of an in vivo Trendelenberg esophageal model for studying questions related to esophageal neuromotor physiology. The Trendelberg esophageal model developed in our laboratory, permits simultaneous recording of circular and Longitudinal contraction of the esophageal musculature in experimental animals. Muscle activity can be measured during peristalsis, vagal stimulation, balloon distention or other events.