62 Background: The expression of immature forms of carbohydrates could help to better understand the biological behavior of gastric cancer. Methods: From a universe of 50 patients with gastric or gastroesophageal junction carcinoma submitted to surgical treatment between January and October 2009, in our department, 36 out of 38 carcinomas ressected during this period, were selected for a tumor tissue immunohistochemical study of the simple mucin-type carbohydrate antigens (Tn, STn, T and ST) and the Lewis carbohydrate antigens (SLea and SLex). Several clinico-pathological parameters were evaluated according to the expression pattern of the antigens studied. Results: The ressected gastric carcinomas presented a high incidence of tissue expression of the simple mucin-type and the Lewis carbohydrate antigens, with all cases presenting expression of at least 2 of the antigens and two thirds the expression of 4 or 5. The correlation between the simple mucin-type carbohydrate antigens was high, just as the same as with the Lewis carbohydrate antigens. The analysis of the clinico-pathological profile of gastric carcinomas according to the expression of these antigens revealed the following associations: Tn with venous invasion and perineural invasion; STn with tumor location and macroscopic form; T with age, gender, tumor dimensions and location; ST with macroscopic form and WHO classification; SLea and SLex with the tumor dimensions. Staging of the tumors also revealed associations with the expressions of these antigens: Tn with serosal invasion, lymph node metastases and stage; STn with lymph node ratio; SLea with serosal invasion and lymph node metastases; SLex with depth wall invasion, lymph node metastases and stage. The antigens T e ST did not reveal differences in the expression pattern according to staging. Conclusions: O-glicosylation alterations of proteins are related with gastric carcinoma, not only their incidence is high but they can also be linked with various clinico-pathological characteristics. The knowledge obtained from this study might serve as a starting point for future investigations taking into account the identification of new biomarkers based on glicosylation alterations of proteins. No significant financial relationships to disclose.