BACKGROUND: The bacterium Helicobacter pylori is strongly associated with the development of gastric adenocarcinoma. Currently, the prevalence in developed countries is 40%, but this value increases considerably in developing countries, which can reach rates bigger than 90%. OBJECTIVE: The objective of this study was to determine the mean and annual prevalence of Helicobacter pylori infection in patients from Itajaí during the period from July 1992 to April 2016, as well as the gender and age groups most affected. METHODS: After consent of the clinical director of the Gastroclinica Itajaí and confidentiality commitment about the research, the database of the Endoscopy Service of the clinic was evaluated. All the patients who underwent their first upper digestive endoscopy with urease test and/or histological analysis were included. The data were submitted to statistical analysis of prevalence by gender, age group and years of study, with subsequent correction through the confidence interval. RESULTS: The mean prevalence of Helicobacter pylori infection thru all years of study was 50.07%. With the calculation of the annual prevalences, it was evident the gradual reduction of infection in the population of Itajaí, that was 81.3% in 1992, declining to 33% in the year of 2016. When classifying the prevalence of infection by gender, it was higher in males (53.59%), and gender distribution by age group showed no statistically significant difference among genders between the ages of 40 and 80 years. In relation to the age group, the highest prevalence was in the group between 40 and 49 years. CONCLUSION: Although this study is retrospective and based on endoscopic database analysis, without access to clinical data of patients such as prior use of proton pump inhibitor and antibiotics to endoscopy, its results are important because they may reflect the current panorama of Helicobacter pylori infection in the city under study, where it has been presenting a gradual reduction of prevalence over the years, with current rates similar to that of developed countries (33%). Future studies are needed to confirm our data.