Three cases of pregnancies complicated by feto-maternal anti-Kell iso-immunisation are presented, as well as a review of the literature. The evolution of new techniques for antenatal diagnosis has made it possible to have a new approach to this fetal pathology. Chorionic villus biopsy can be carried out in the first trimester of pregnancy when there has previously been a serious incidence of anti-Kell immunisation with a couple where the husband is heterozygous for the Kell antigen. In the second and third trimesters the surveillance of the patient is essentially dependent on ultrasound examination of the fetus and placenta, which makes it possible to detect hydropic changes, and also depends on blood sampling from the cord which makes it possible to assess by direct measurement the degree of fetal anaemia. Now pulsed Doppler must be added to these classical diagnostic techniques because it allows a gross estimation of fetal haematocrit levels.