To assess the anatomic relationships between areas of dysplasia and "early" carcinoma, we evaluated histologically the entire mucosal surfaces of seven esophagectomy specimens resected for high-grade dysplasia or early invasive (intramucosal and submucosal) carcinoma. We developed surface area maps and assessed the various degrees of dysplasia or carcinoma at 10 equidistant points. Our analysis shows an equal likelihood of high-grade dysplasia and/or early invasive carcinoma occurring throughout the length of Barrett's epithelium. Foci of carcinoma appear within fields of Barrett's epithelium and adjacent to areas of dysplasia, supporting a dysplasia-carcinoma sequence. The amount of dysplastic epithelium appears related to the surface area of Barrett's epithelium present. However, we found no association between the extent of dysplasia and the likelihood of finding carcinoma. This study supports the current standard of practice for clinical surveillance of patients with Barrett's esophagus by uniformly distributed endoscopic biopsy of the complete length. In addition, the presence of any degree of dysplasia may be an indication for close clinical follow-up.