A lower esophageal sphincter tightening device for treating gastroesophageal reflux disease which includes an insertion device, an energy source, and an energy transmitting device. The insertion device, by insertion through a body opening, positions the energy transmitting device in the proximity of the lower esophageal sphincter. The energy source generates and transmits energy via the insertion device to the energy transmitting device which directs the transmitted energy onto the lower esophageal sphincter which is comprised largely of collagen. The energy source transmits energy at a level sufficient to cause heating of the sphincter's collagen resulting in a shrinkage of the collagen and a tightening of the sphincter.