The effect of the H2 receptor antagonists, cimetidine and ranitidine, on Barrett's esophagus was assessed in a retrospective study. There was no evidence of regression of Barrett's epithelium in the 22 patients treated for a mean of 13 months with 800-1,600 mg/day cimetidine, or in the 13 patients treated for a mean of 5.7 months with 300 mg/day ranitidine. Eight of 12 esophageal (Barrett's) ulcers healed on cimetidine therapy over a mean period of 8.7 months, and eight of nine esophageal ulcers healed on ranitidine therapy over a mean period of 3.5 months. We conclude that short-term treatment with H2 blockade does not cause regression of Barrett's esophagus, although such treatment can heal esophageal ulcers.