Method/devices for endoscopic laser treatment of gastrointestinal disorders such as, gastro-esophageal reflux disorder (GERD) are disclosed. Treatment involves irradiating tissue of the digestive tract to strengthen muscle tone and shrink anatomical areas reducing occurrence of reflux of food/liquids from the stomach to the esophagus. In a preferred embodiment, equipment comprises a gastro-endoscope with a working channel for inserting an optical fiber. Laser device comprises a diode laser source emitting a suitable wavelength and wave pattern through optical fiber. Laser radiation is applied near the Z line at the esophago-gastric junction. Measures are taken to assure irradiation is very accurate. Injury to the mucosa and adjacent structures, e.g. nerves, are avoided by focusing at the muscularis layer while preventing thermal effects on mucosa. This is achieved using wavelengths of ca. 1470 nm or ca. 980 mm. Energy is emitted perpendicular to fiber axis using optical fibers with side fiber distal tips, radial fiber distal tips or twister fiber distal tips.
