In order to characterize the differentiation of endocrine cells present in Barrett's oesophagus and to determine if they express a single or multiple hormonal pattern, endoscopic biopsies were taken from both the lesion and the fundus of 45 patients and studied at the light microscopical level. Conventional histology revealed three different epithelial patterns: gastric atrophic fundic, intestinal and junctional. A mixture of these patterns was present in 28 cases (62%) and the single type was identified in 17 cases (38%). The use of three silver staining methods and antibodies to human chromogranins allowed us to identify numerous endocrine cells in all but 1 case. Eleven sera against all the most common hormones stored in the endocrine cells of the gut were used to identify the main products of the cells. The following immunoreactivities were identified: 5-hydroxytryptamine (5-HT) (in 75% of the studied cases), somatostatin (87%), motilin (31%), pancreatic polypeptide (PP) (20%), glucose-dependent insulinotropic polypeptide (20%), gastrin (15%), glucagon (15%), peptide tyrosine tyrosine (13%), secretin (7%) and neurotensin (2%). No cholecystokinin-immunoreactive cells were identified. Our results indicated that, in Barrett's epithelium, both gastric and intestinal endocrine cells differentiate, in accordance with the variability of differentiation in the non-endocrine cells present in the different types of columnar epithelium. These findings provide support for the conclusion that Barrett's epithelium arises from a pluripotential stem cell capable of both gastric and intestinal differentiation.