Background: There is a large amount of evidence that the ABO blood group system may play a role in disease etiology. A relationship between ABO and Rhesus blood groups and cancer risk has been demonstrated in a number of studies. However, in relation to gynecological malignancies, these findings are inconsistent and contradictory. Aim: To perform a case-control study for analysis of the distribution of ABO and Rh blood antigens among women from South-East Siberia who suffered from ovarian, endometrial and cervical cancer, and to assess the potential role of these antigens in carcinogenesis. Design, Subjects and Methods: A total of 1,163 cases with ovarian cancer (n=551), endometrial cancer (n=440) and cervical cancer (n=172) were involved in the study. The control group was formed from 22,581 female blood donors. Blood groups were determined through patients medical records and blood donor records. Odds ratios (OR) with 95% confidence intervals (CI) were calculated. The blood group O was defined as the referent group, as it has the greatest frequency in the populations of Southern Siberia. P values less than 0.05 were regarded as statistically significant. Results: We found that carriage of non-O blood types increased the risk of ovarian cancer by 40-60%, and the magnitude of this relationship was strongest in women with the AB (IV) blood group. Carriage of the A (II) blood group strongly correlated with an increased risk of ovarian cancer in premenopausal, but not in postmenopausal women. No statistically significant correlations were obtained for endometrial cancer and cervical cancer. Additionally, we did not observe a relationship between Rhesus factor and cancer risk. Conclusion: We suggest that carriage of non-O blood groups may elevate risk of ovarian cancer and can play a role in its development.