Immunohaematological tests used in antenatal patients have come a long way. However, despite a great deal of progress, we should not loose sight of the fact that these tests give only an indirect measurement and will only help the obstetrician, in conjunction with other fetal parameters, to assess the severity of the haemolytic disease (HD) of the fetus and newborn. The best method to assess the severity is the direct determination of foetal blood group hemoglobin after foetal blood sampling but this procedure is not without risk. Since 10 years ago, it is possible to determine the RHD genotype of the fetus using amniocytes and, today, maternal plasma directly. All pregnant women should be grouped for ABO-RH-KEL1 and the sera tested for clinically irregular antibodies (anti-RH are still the most frequent). The trend in anti-RH levels is more important than the level itself. The perfect technique for anti-RH quantitation has not been developed. Manual titration is simple but only provides rough, semiquantitatives estimates of anti-RH concentration. Quantitative haemagglutination methods, using auto-analyzers and appropriate anti-RH1 standards, measure in microg/ml, are sensitive, rapid and have acceptable intra-laboratory reproductibility.