The AB0 system has been established as a risk factor or protection associated with the development of multiple pathologies. Thus, the search continues for its association with other diseases. The objective of this study was to determine the association between the AB0 blood system and leukemias. Blood samples were obtained from 102 patients with a presumptive diagnosis of leukemia. We carried out an AB0 typification with Gel-cards. The morphological classification of leukemia was based on the identification of the cellular line and its differentiation stage by means of a peripheral blood smear with Wright staining. The statistical analysis was performed with SAS/STAT® ver. 9.2 statistical software. The X2- Pearson test was utilized for determining the association between two variables. An association was found of AB0 blood groups and leukemias of acute presentation, reporting more cases of those expected for AML in patients with AB blood group and a greater proportion of ALL in those with blood groups A, B, and 0 [X2.-Pearson=102; df=3; p=0.001]. More cases were reported than those expected of CML in patients with blood groups B and CLL than in persons of group 0 [X2-Pearson=6.604; df=1; p=0.017]. According to age group, an association was found of pediatric patients with ALL and adult patients with CLL (X2-Pearson=8.860; df=3; p=0.03). According to the study, the AB0 blood system is associated with leukemias of acute presentation.