In order to evaluate the testing proficiency in immunohematological laboratories in Croatia blood samples were prepared and fully examined in the Croatian Institute for Transfusion Medicine and sent to all the transfusion laboratories in the country. The laboratories were asked to perform the following tests: determination of AB0 blood group and Rh phenotype; detection and identification of irregular antibodies and crossmatches between serum and RBCs. All the laboratories (100%) accurately determined AB0 and Rh(D) negative blood groups and crossmatch between compatible serum and RBCs. In 80.65% of the laboratories, Rh(Du) blood group was accurately determined. The incompatibility between serum and Rh(Du) RBCs in crossmatch was detected in 93.55% of the laboratories. 96.77% laboratories correctly detected irregular antibodies. Only 35.48% of the laboratories accurately identified anti-D and anti-C alloantibodies in the serum, 32.26% failed to identify one of the two antibodies and 29.03% of the laboratories detected irregular antibodies but did not identify their specificity. Only 35.48% of the laboratories correctly performed all the tasks.