Genetic factors may play a role in prediction of gastrointestinal side effects of aspirin, one of the most used drugs worldwide. We aim to determine a possible correlation between AGT A-20C (rs5050) gene polymorphism and gastro-duodenal ulcer in patients taking low-dose aspirin, adjusted for clinical and histological characteristics.Results. We enrolled 211 patients stratified according to 83 AC and 6 CC patients. There were no significant differences regarding demographical and clinical parameters, except for the frequency of ulcers (4%, 8.4% respective 50%, p=0.03), endoscopic bleeding signs (12.3%, 14.5% respective 50%, p=0.0001) and the frequency of gastritis in biopsy (63.9%, 54.2% respective 16.7%, p=0.03) (OR:9.66, p=0.04) than AA group, as well as variant C allele compared with normal A allele (OR: 2.12, p=0.04). On multivariate analysis, variant homozygous CC genotype p=0.02) for ulcer, while H. pylori infection (OR:2.40, p=0.04) de ulcer (OR:9.66, p=0.04) fața de grupul cu genotip AA, iar alela mutantă C s-a corelat cu un număr mai mare de ulcere decât alela normală A (OR: 2.12, p=0.04). Genotipul homozigot mutant CC pentru polimorfismul p=0.02) pentru apariția ulcerelor, în timp ce infecția cu H. pylori (OR:2.40, p=0.04)