We have previously reported that endoscopic sclerosis of the gastric cardia is an effective treatment for experimental gastroesophageal reflux in dogs. The histologic effect of endoscopic sclerosis is limited to the proximal stomach; mucosal deformity provides endoscopic evidence of sclerosis, and the intramural effects are shown by ultrasonographic technique. This report describes histologic and ultrasonographic results in the dogs at the completion of endoscopic sclerosis. This report also describes the endoscopic ultrasound results in the first two patients who have completed endoscopic treatment for reflux by means of endoscopic sclerosis of the gastric cardia. All canine and human subjects had sonodense lesions involving all layers of the proximal stomach at the injection site at the conclusion of treatment. Histologic examination of canine tissues showed dense submucosal and muscularis fibrosis in the stomach; the esophagus was normal. Endoscopic ultrasound demonstrates the effect of endoscopic sclerosis; this technique may be useful in the evaluation of symptomatic responses after this treatment.