Serum anti-(GalNAcβ) and anti-para-Forssman disaccharide (PF(di), GalNAcβ1--3GalNAcβ) IgG levels were earlier found to be related to histological grading and progression of gastrointestinal cancer. To study the relation of serum antibodies level to survival in patients with gastrointestinal cancer. The level of anti-GalNAcβ, and PF(di) IgG was analysed in the serum of patients with gastric (n = 78) and colorectal (n = 48) cancers in the long-term follow-up using ELISA with polyacrylamide glycoconjugates. Survival rate and hazard ratio (HR) were assessed by the Kaplan -- Meier method and Cox univariate analysis in different patho-morphological groups. Better survival was observed in patients with an increased preoperative level of GalNAcβ antibodies. These were the gastrointestinal group in stages II, III or tumors T2--4 (n = 90--104, P = 0.007, HR = 0.48--0.49, 95% CI 0.27--0.83, and the group with gastric cancer in stages I, II (n = 49, P = 0.051, HR = 0.39, 95% CI 0.14-1.04). The survival time was significantly longer in the gastrointestinal group in patients whose GalNAcβ antibodies level rose in dynamics (stage III or N1--2: p = 0.031--0.039, HR = 0.29--0.31, 95% CI 0.09--1.00). No significant difference in survival of patients was observed in the evaluation of PF(di) antibodies. We suggest that the level of antibodies and its change reflect the enteric microbiota colonization, which may influence cancer progression via different interrelations between microbiota, the tumor and immune system. The preoperative level of GalNAcβ antibodies and its dynamics may be of prognostic significance for clinical outcome assessment.