Background: The finding of a hiatal hernia is usual during upper gastrointestinal endoscopies. However the correlation of symptoms, manometric and radiological findings with the endoscopy report is far from clear. Aim: To assess radiological findings, 24 pH measurements, esophageal manometry and symptoms among patients in whom a hiatal hernia was found during an upper gastrointestinal endoscopy. Material and Methods: One hundred fifteen patients aged 23 to 82 years (77 women), with an endoscopic diagnosis of a hiatal hernia of more than 5 cm were studied. An esophageal manometry and 24 hour pH determination were carried out. Results: Hiatal hernias type I, II, II and IV were found in 50, 12, 38 and 15 patients of similar age, respectively. Gastroesophageal reflux symptoms were more common among patients with hernias type I and III. Mechanical symptoms such as retrosternal pain were more common in type IV hernias. Manometry showed a hypotensive sphincter in 100 and 78% of patients with hernias type I and III, respectively. An abnormal 24 hour pH measurement was found in 95 and 85% of patients with hernias type I and III, respectively. Conclusions: Functional studies show a high frequency of pathological acid reflux among patients with hiatal hernias type I and III.