An endoscopic survey was undertaken in northern Iran to identify and determine the prevalence of possible precancerous lesions of the oesophagus. 218 men and 212 women, aged between 15 and 70 years, were included in the study. Oesophagoscopies were done on all 430 subjects and biopsies on 418. A chronic oesophagitis, involving mainly the middle and lower thirds of the oesophagus, was found in 80% of the subjects, and the frequency was very high even in the younger age-groups. Clinically and histologically the oesophagitis in this rural population was different from that observed in the low-risk areas of Europe and the United States, where oesophagitis is often associated with reflux. Dysplasia was diagnosed in 16 subjects and invasive carcinoma in 11. The very high prevalence of chronic oesophagitis in northern Iran, where a high incidence of oesophageal cancer has also been reported, suggests that these two lesions are associated.