In order to correlate histopathology and cell turnover in esophageal tissue in patients with esophageal columnar epithelium, biopsy specimens from 11 patients were studied. Two of the patients had adenocarcinoma of the esophagus not present in the specimens studied. In the heterogeneous esophageal columnar epithelium, the DNA synthesis phase averaged 10.4 +/- 0.3 hr; labeling index of cells in the crypt-like structures was 23.3 +/- 0.3%; generation time was 44.6 +/- 1.2 hr, and the mitotic index was 1.82 +/- 0.07%. Significant differences were not present among specimens with columnar epithelium but they differed from cell proliferation in adjacent squamous epithelium where S phase was similar but labeling and mitotic indexes were lower and generation time increased to 105 +/- 6 hr. In the 2 patients with adenocarcinoma of the esophagus, and in 1 of 9 without adenocarcinoma, labeling of surface columnar cells after brief exposure to [3H]thymidine was present suggests that this may be a manifestation of early malignant change.