Small numbers of intraepithelial esophageal eosinophils (IEE) may be seen in 50% of patients with gastroesophageal reflux disease and occasionally in normal volunteers. High concentrations of IEE are rarely seen in either setting. During a two-year period we identified 12 adult patients with very dense eosinophil infiltrates in esophageal biopsies (defined as > 20 IEE/high-power field). Dysphagia was the presenting complaint in each, but no evidence of anatomical obstruction could be found. Endoscopic esophagitis was absent, but biopsy showed marked squamous hyperplasia and many IEE. Eleven patients had normal esophageal acid exposure on 24-hr pH monitoring. Esophageal manometry showed a nonspecific motility disturbance in 10 patients. For comparison, 90 patients with excess esophageal acid exposure on 24-hr pH monitoring were studied. Thirteen (14%) had motility disturbance, and 21 (23%) had dysphagia. Esophageal biopsies were devoid of IEE in 47 patients; none of the 43 with IEE had infiltrates as dense as those seen in the 12 study patients. The presence of high concentrations of IEE in esophageal biopsies from patients with dysphagia, normal endoscopy, and normal 24-hr esophageal pH monitoring represents a distinctive clinicopathologic syndrome not previously described.