Chronic esophagitis and the subsequent morphological changes of the esophageal mucosa were histologically studied in esophagectomy specimens from 15 patients with Barrett's esophagus. Basal layer hyperplasia with papillary elongation, intraepithelial eosinophils, and intraepithelial neutrophils were found in the squamous epithelium of all (100%), 7 (46.7%), and 14 (93.3%) of the 15 specimens, respectively. Moreover, a specialized type of Barrett's mucosa was found in the metaplastic columnar lining of all the specimens. The muscularis mucosae appeared intact beneath the squamous epithelium lining the proximal esophagus in 13 specimens (86.7%), while it became thick and "dual" beneath the metaplastic columnar epithelium lining the distal esophagus in 14 specimens (93.3%). This dual muscularis mucosae, as well as the metaplastic columnar epithelium, particularly the specialized type, may be part of the specific histological changes characteristic of Barrett's esophagus.