One hundred and three patients were included in the study. Thirty seven had duodenal ulcer (DU) (Group I), 35 DU with gastric outlet obstruction (GOO) with presence of an active ulcer in the duodenum (Group II). Thirty one had DU with GOO but no active ulcer (Group III). Presence of H. pylori infection was determined by urease test, serology and/or histology. The prevalence of H. pylori in these groups was compared. Levels of Anti-H. pylori IgG antibody titres were also compared. The patients with duodenal ulcer (DU) were significantly younger (38 +/- 2 years) compared to those with established gastric outlet obstruction without ulcer (45 +/- 2 years) (P = 0.02). The prevalence of H. pylori infection in DU (95%), DU with GOO with ulcer (91%) and DU with GOO but no ulcer (90%) was not significantly different (p > 0.05). Anti-H. pylori IgG antibody titre levels were 72 +/- 6 EU/ml in Group III. The titre levels between Group I and Group III were significantly different (P < 0.05). The prevalence of H. pylori infection is high is patients with DU and is unaltered by gastric outlet obstruction. The presence or absence of an active ulcer with gastric outlet obstruction does not affect its association with H. pylori infection.