Using an inflatable balloon catheter with an abrasive, absorbent surface, cytologic material was collected from the whole esophageal mucosa of 500 patients, none of whom were suspected of having esophageal cancer. Cytology identified malignant cells in 15 patients and dysplastic cells in another 26. All lesions were confirmed histologically by endoscopically directed biopsies. Ten cancers were early-stage lesions. The cytologic findings are reported in detail.