Data concerning the prevalence of Helicobacter pylori (H. pylori) in diabetic patients are scanty and controversial. The aim of this study was to evaluate the prevalence of H. pylori infection in patients with diabetes mellitus (DM), and to assess whether the presence of bacterium was associated with severity of dyspeptic symptoms and endoscopic findings in such patients. The study involved 42 patients (19 men, 23 women; mean age 55 years, range 34-75 years) with DM and dyspeptic symptoms. Sixteen patients (38%) were classified as having type 1 diabetes and 26 (62%) patients as having type 2 diabetes. All patients had chronic dyspepsia, and each patient has completed a self-report questionnaire to obtain information concerning the presence and severity of upper gastrointestinal tract symptoms. H. pylori status was confirmed by 13C-urea breath test (13C-UBT), and diabetic patients underwent upper gastrointestinal endoscopy. Twenty-six (61.9%) of patients with DM were positive for 13C-UBT. There were no statistically significant differences in the infection rate between patients with type 1 and type 2 diabetes, and the prevalence of H. pylori infection was not associated with the known duration of diabetes. There was no significant difference in the symptoms score between H. pylori-positive and H. pylori-negative diabetic patients, and endoscopic findings in patients with DM were in the same range with those found in dyspeptic subjects from the same region. In conclusion, H. pylori infection is not associated with DM, duration of diabetes, or severity of dyspeptic symptoms in patients with DM.