Introduction: Transfusion medicine is part of the laboratory and clinical medicine that deals with the treatment of patients who produce the preparations that characterize the bloodstream. Blood groups are hereditary properties found on blood cell membranes: erythrocytes, leukocytes, platelets and blood plasma proteins and are determined for each individual recipient during the immunoreceptor test. All immunofluorescence testing procedures must be strictly defined, and the manner of carrying out the assurance and control of the quality of testing, as well as conducting the documentation, must be described in detail in the sequence of procedures (algorithms), operating instructions and / or standard operating procedures. Aim: The aim of this paper is to determine the total number of errors during the immunohematological testing in the period 2013-2016. In the Center for Transfusion Medicine, to determine the percentage of errors in relation to the total number of immunofluorescence tests, to sort errors into administrative, pre-analytical and analytic, and to share errors with those with consequences and no consequences Methods and Subjects: In this retrospective study, signs of adverse events were screened in the pre-analytical and analytical part of the immunohematological treatment of blood volunteer blood donor blood samples for the period 2013-2016 and were divided into administrative, pre-analytical and analytical. Results: At the Center for Transfusion Medicine in the period from 2013 to 2016. Total immunofluorescence tested 75651 DDK. There were 37 errors in the immunohematological test. There were 6, 21 in the analytical part of immunohematological diagnosis, and 10 administrative mistakes in pre-analytical white. By sharing a mistake with those with consequences and no consequences. There were a total of 3 misalignment errors and 34 unsuccessful. The consequences were subsequently proved to be a positive result of IAT and the destruction of all blood doses of that DDK and the case when Rh D (-) DDK was not "weakened" D. In the absence of the error group there were observed incorrectly entered erythrocyte DDK antigens (10), Equipment faults resulting in destruction of test reagents (5), destruction of reagents due to error (3), replacement or unlabeled DDK (6) sample, and non-conformation to test performed and reported (10). Conclusion: The error in the immunohematological part of DDK testing at KBC-Split is rare, that is, their frequency is as well as in more developed centers. Only one mistake was a consequence, and no mistake in the immunohematological part of testing did not endanger death or endanger the health of the patient.