The aim of this study was to establish the prevalence of H. Pylori infection in patients with chronic gastroduodenal pathology, who were treated in the gastroenterology units of four hospitals located in the Federal Capital and its neighbouring areas. 398 patients were studied by means of clinical assessment and epidemiology data. Upper endoscopy was carried out two biopsies were taken of the gastric antrum for a quick ureasa test and histological assessment of the H. pylori state by means of giemsa's stain. The prevalence of infection on the total of the studied population was 75.6%. In patients with gastric ulcer was 70%; in patients with duodenal ulcer it was 77.2% and 78.5% in patients with chronic gastritis. The prevalence of H. Pylori infection on the population according to age groups was: 61.54% in patients between 21 and 40 years; 76.14% in patients between 41 and 60 years, and 68.22% in patients over 60 year. We have tried to obtain a correlation between the prevalence of the infection and some sanitary characteristic (Running water and sewers) on the studied population. It was seen that 225 patients who lived in dwellings with running water and sewers showed a prevalence of infection of 69.34% and in 129 patients who did not have running water or sewer the rate of prevalence of infection was 83.72; a difference which was statistically significant, (with P < 0.01) for the patients who lived in poor sanitary conditions. These data may be important when the design of therapeutic schemes for the eradication of the bacteria is made.