We present in this paper our experience in the routine use of an automatic reader for microtiter plates (IBG Systems). A total of 2044 samples from blood donors have been tested for ABO (haematic and seric) and Rh (D antigen) blood group typing. The red blood cell samples have been tested against monoclonal anti-A, anti-B, anti-AB and anti-Rh 1 (D) sera (using two different anti-D reagents). As a negative control, 3% albumin solution was employed. In order to determine the seric groups, the plasma samples were tested against A1, A2, B and 0 cells. In all cases the red cells were suspended in Ficoll 400R-Methyl cellulose (FMC), and 0.01 Bromelin was added to red blood cell samples to be typed. The obstacles in the automatic readings were mainly solved by visual reading of the microplates. In the 2,044 samples analysed with the automatic reader, 19 discrepancies (0.94%) were found in ABO typing. In all cases the error was in the seric blood group. Three false positive reactions were found with 0 red cells. Two false negative with B red cells, interpreted by the automatic reader as doubtful results. Three positive readings were detected, in one case the positivity was due to alloantibodies (C + D specificities), the other two cases were autoagglutinations. False negative reactions were found, in 11 cases, 8 of them due to lipaemia and the remaining three were haemolysed plasma samples. It should be stressed that out of 19 cases of discrepancy, only 5 (0.24%) were due to the automatic reader while the remaining were due, to sample troubles.(ABSTRACT TRUNCATED AT 250 WORDS)