Eleven subjects with a previous diagnosis of columnar lined esophagus and 12 control patients underwent esophagogastroduodenoscopy, including vital staining with Lugol's iodine and biopsy. Histology in 47 of 48 biopsies from controls agreed with endoscopic findings, and no patient had a columnar lined esophagus. Of 60 biopsies taken from study patients, the endoscopic appearance in 8 (13%) was not consistent with the histology. Good agreement was demonstrated between endoscopy and histology (kappa = 0.72). Compared with histology as the reference measure, the sensitivity, specificity, and accuracy of endoscopy were 89%, 93%, and 91%, respectively.