Full blood transfusions in veterinary medicine have become increasingly common and are integral part of the treatment of critically ill animals. Common situations involving transfusion are anemia that endangers life from acute bleeding or surgical loss of blood, hemolysis from drugs or toxins, immune mediated disease, severe regenerative disease, and neonatal nerve enterotrexis in kittens. Correction of erythrocyte is necessary when hematocrit suddenly falls below 20% in dogs or less than 12-15% in cats, if more than 30% of total blood volume is lost, if blood loss leads to collapse, bleeding is increased and in cases where Standard anti-shock therapy does not produce results. The dog can be positive or negative for each blood group in an international standard DEA system. The only exception is DEA 1 because it consisted of a variety of alleles (DEA 1.1, DEA 1.2 and DEA 1.3). Dog can be either positive to one of three subgroups or negative to all three. Blood Group DEA 1.1. Antigen is the strongest and most clinically important. Frequency of Blood Group DEA 1.1. In different assays ranged from 33% to 67%, depending on the breeds. There are several ways how to determine blood groups in dogs, crossmatching methods and blood typing methods on appliances and test cards. The crossmatching method for determining blood compatibility is a simple method, easy to perform and safely reduces the risk of hemolytic chiral fusion reactions.