The aim of this work was to analyze the elastic fibers and collagen fibers of the gastroduodenal junction in rats at different ages. Through histomorphometric search, data on changes in connective tissue due to aging were obtained in order to understand its anatomical and functional relationships. Materials and Methods: We used 34 male rats divided into two groups: adult (03 months) and old group (18 months). To observe the connective tissue fibers of gastroduodenal junction, conventional histological techniques were applied and stained with the Verhoeff’s iron hematoxylin and Weigert’s resorcin fuchsin; Weigert’s resorcin fuchsin after oxidation with 1% aqueous solution of oxone, Picrosirius and hematoxylin-eosin. Slides were analyzed with the program Image Pro-Plus. Results: Our results indicate that during aging the linear density, oxytalanic elastic fibers and mature elastic fibers decreased in the old group compared to the adult group, since the elaunin fibers had its linear density increased in the old group. Regarding the linear density of collagen fibers, they did not show statistically significant differences.