In 19 asymptomatic subjects, a total of 95 mucosal suction biopsies were taken from multiple sites in the distal 10 cm of esophagus. The biopsies were examined for evidence of basal cell hyperplasia and elongated dermal papillae, features considered to be histological consequences of gastroesophageal reflux. Fifty-seven per cent of the biopsies in the distal 2.5 cm of the esophagus and 19% of the biopsies above 2.5 cm exhibited these histological features.