The precise role of Helicobacter pylori infection in gastroesophageal reflux disease (GERD) is a matter of intense debate. Twenty-four-hour esophageal pH monitoring has a higher accuracy than endoscopy for the diagnosis of GERD, but the correlation between H. pylori infection and esophageal pH-metric parameters has almost never been assessed. Therefore, we evaluated the relationship between the infection and the presence of disturbances not only in endoscopy but also in 24-hour esophageal pH monitoring. One hundred consecutive patients undergoing 24-hour esophageal pH monitoring because of symptoms suggestive of GERD were included in the study. Esophageal manometry was carried out to study the position and the pressure of the lower esophageal sphincter (LES). Prevalence of H. pylori infection was evaluated by histology (hematoxylin and eosin stain) and rapid urease test. The mean age of the patients was 50 +/- 15 years; 50% were men and 56% had an abnormal pH-metry (DeMeester score more than 14.7). The prevalence of H. pylori in patients with abnormal pH-metry was 57% (95% CI, 42-70%) and was 52% (95% CI, 39-64%) in those with normal pH-metry (nonsignificant differences [NS]). In the multivariate analysis, H. pylori infection did not correlate with an abnormal pH-metry (odds ratio, 0.8; 95% CI, 0.4-1.8; NS). The proportion of cases with abnormal pH-metry among infected patients was 54% (95% CI, 41-66%) and was 59% (95% CI, 44-72%) among uninfected patients (NS). Mean values of pH-metric parameters (+/-SD), respectively for H. pylori-positive and -negative patients, were total score (30 +/- 33 vs. 36 +/- 38), number of reflux episodes (7 +/- 7 vs. 11 +/- 11), number of episodes more than 5 minutes (3.7 +/- 5 vs. 3.8 +/- 5), longest reflux episode (2.4 +/- 2 minutes vs. 3.1 +/- 3 minutes), and fraction time (%) with pH less than 4 (total, 6 +/- 7 vs. 6.8 +/- 8; upright, 3.9 +/- 4 vs. 4.5 +/- 5; supine, 7.4 +/- 12 vs. 7.2 +/- 10) (all findings were NS). Endoscopic findings, respectively for H. pylori-positive and -negative, were hiatus hernia (41% vs. 41%), endoscopic esophagitis (Savary-Miller) (54% vs. 46%), and Barrett's esophagus (15% vs. 11%) (all findings were NS). Finally, differences were not demonstrated in the pressure of the lower esophageal sphincter (12 +/- 8 mmHg vs. 14 +/- 12 mmHg) among H. pylori-positive and -negative patients. H. pylori infection is not associated with gastroesophageal reflux disease, as evaluated endoscopically and with 24-hour esophageal pH monitoring.