The Angelchik anti-reflux prosthesis, a C-shaped, silicone filled device surgically secured around the distal esophagus, received premarket approval by the Food and Drug Administration's Bureau of Medical Devices in 1979. Despite its use in over 9000 patients, there are few physiologic data documenting its effectiveness. We studied ten patients before and 3 months after prosthesis implantation with barium meal, endoscopy, esophageal biopsy, standard acid reflux testing, esophageal manometry, gastroesophageal scintigraphy, and symptom scoring. After surgery all patients were able to discontinue cimetidine and elevation of the head of the bed. Two patients had documentation of mild reflux, one of whom needed to have the prosthesis removed because of its herniation into the mediastinum. Eight patients had no reflux. There was statistically significant improvement in endoscopic, symptomatic, and biopsy grading as well as increased lower esophageal sphincter pressure after surgery. Prosthesis implantation is a promising surgical treatment of intractable esophageal reflux, but we believe additional and long-term studies are needed before its general use.