Direct antiglobulin test (Coombs test) is used for the detection of antibodies or complement components on the red cell membrane. The result of a positive DAT in voluntary blood donors is extremely rare. The aim of our case studies was to demonstrate that the positive DAT in voluntary blood donors can be the cause of disturbances during the performance of compatibility test (crossmatch), in patients with multiple erythrocyte alloantibodies. For performing DAT we used polyspecific and monospecific AHG reagents anti-IgG, anti-C3d (Seraclone®) for the method in a test tube, and the ID Liss/Coombs card anti-IgG + C3d (Diamed®) for the gel method. During the performance of the compatibility testing, for the haematological patient who has the anti-K and antiE irregular antibodies in the serum, with phenotype blood unit, the positive result was obtained at room temperature and in the indirect antiglobulin test. In further examination, the donor red cells were tested in the direct antiglobulin test. In a test tube with poliyspecific AHG reagent test result was positive, and in the LISS/Coombs gel method test result was negative. Because of discrepancies in testing, DAT was performed with monospecific AHG reagents. Only with anti-C3d monospecific AHG reagent in tube there was a positive result with donor erythrocyte. Voluntary blood donor was a man, 61 years old, who was suffering from hypertension, treated by ACE inhibitor medication. The results of blood counts and biochemistry did not indicate existence of haemolytic process. Aetiology and consequences of positive DAT in the healthy population are not yet sufficiently investigated. This requires extensive and detailed research. Accordingly, the disturbances in the selection of blood units for the recipient should be kept in mind the existence of this phenomenon.