We evaluated in children with abdominal complaints the prevalence of Helicobacter pylori gastric and duodenal colonization and the histological features of gastric and duodenal mucosae. Fifty patients, aged 1-17 years, underwent upper endoscopy for recurrent abdominal pain, vomiting and/or gastrointestinal bleeding. With serological, bacteriological and/or histological methods twenty-eight children were demonstrated to be Helicobacter pylori-positive. No statistically significant differences were observed with regard to age, sex and indication to perform endoscopy. Eighty-two percent of Helicobacter pylori-positive patients had gastritis and/or duodenitis. The Helicobacter pylori-positive children had higher Helicobacter pylori specific IgG levels than the Helicobacter pylori-negative ones (p < 0.001). No statistically significant differences were found between Helicobacter pylori-positive and Helicobacter pylori-negative subjects, for gastrin and pepsinogen I. Since the frequency of Helicobacter pylori infection in children with gastrointestinal complaints is high, in patients undergoing upper endoscopy, the sistematical examination of bioptic samples for bacteriological and histologic procedures is of great importance.