Background & Aims: Treatment for gastroesophageal reflux may be ineffective in patients with an eosinophilic infiltration of the esophagus. The aim of this study was to investigate whether unremitting symptoms of gastroesophageal reflux and biopsy abnormalities of the esophagus may be associated with the ingestion of certain foods., Methods: Ten children previously diagnosed with gastroesophageal reflux by standard testing with long-standing symptoms (median, 34.3 months; range, 6-78 months) despite standard antireflux therapies, including Nissen fundoplication in 6 patients, were fed the elemental formulas Neocate or Neocate-1-Plus (Scientific Hospital Supplies Inc., Gaithersburg, MD) for a minimum of 6 weeks. Each child had repeat endoscopy followed by open food challenges., Results: While receiving the formulas, patients had either resolution (n = 8) or improvement (n = 2) of symptoms. On follow-up esophageal biopsy, the maximal intraepithelial eosinophil counts decreased significantly before (median, 41; range, 15-100) to after (median, 0.5; range, 0-22) the formula trial (P = 0.005). Other reactive epithelial changes of the esophageal mucosa also improved significantly. All patients redeveloped their previous symptoms on open food challenges., Conclusions: Chronic gastrointestinal symptoms and histological changes of the esophagus unresponsive to standard treatments for gastroesophageal reflux were improved by the use of elemental formulas. Symptoms recurred when specific dietary proteins were reintroduced during open food challenges. The mechanism of these observations is unknown.