Histological and histochemical evaluation of 33 biopsies and 8 distal esophagectomy specimens revealed specialized columnar epithelium with intestinal features [intestinal metaplasia (IM)] to be the most common type (91%) of metaplasia in Barrett's esophagus (BE). Junctional epithelium was found in only 3 of the 33 biopsies. The type III subvariety of IM (TIII-M), characterized by the presence of sulfomucins in the non-goblet columnar cells, was found in 58% of all our biopsies and 62% of operative specimens. Six of the 7 cases of epithelial dysplasia were associated with TIII-M; one of them subsequently developed an adenocarcinoma. The transitional epithelium adjacent to adenocarcinomas in the operative specimens also showed TIII-M in five of six cases. Our findings indicate that TIII-M is almost as common in Barrett's-associated carcinoma as in nonneoplastic cases of BE, thereby limiting the usefulness of this histological marker as an indicator of neoplastic change (P = 0.5). On the other hand, TIII-M seems to be significantly associated with mild dysplasia in BE. The value of TIII-M as a prognostic indicator regarding the subsequent development of esophageal carcinoma remains in doubt and could be more precisely assessed by a prospective study.