The relationship between reflux esophagitis and hiatal hernia was studied using fiberoptic endoscopy. Of 293 patients having upper-gastrointestinal endoscopy during an 18-month period, 64 (22%) had a hiatal hernia and 38 (13%) had esophagitis. Half the patients with a hiatal hernia had esophagitis, whereas the vast majority (84%) of patients with esophagitis had a concomitant hiatal hernia. The association between esophagitis and hiatal hernia was highly significant (P less than 0.0001). There was no statistically significant association between the size of the hiatal hernia and the degree of esophagitis on endoscopy. A permissive role of hiatal hernia in the genesis of reflux esophagitis is suggested.