Aim: 1) We have presented our experiment conducted to detect anti-K antibodies from the Kell-system in pregnant women and their connection with potential destruction of foetal red cells, which may result in haemolytic disease of the foetus and the newborn (HDFN). 2) We have also indicated serological and molecular methods important for a proper diagnosis. Material and methods: 27 women with anti-K. Serological diagnosis of K antigen in fathers and children. KEL1 gene examination in foetuses from DNA isolated from foetal cells contained in amniotic fluid, using discrimination of alleles - real-time PCR method. Results: Anti-K were detected in most women after blood transfusion, the fathers were usually K negative. Foetomaternal incompatibility was found in 6 out of 27 women. Haemolytic disease was observed in 5 cases: 3-severe, 1-fatal, 1-mild. Foetal genotyping allowed us to avoid cordocentesis in two pregnant women, it appeared that both foetuses have not received KEL1 gene from heterozygous (Kk) fathers – in the previous pregnancies the children had died because of HDFN. Conclusions: 1) In every pregnant woman with anti-K, the K antigen should be examined in the father. 2) In every K+ father the phenotype should be evaluated and if he is heterozygote (Kk), the fetal KEL1 gene must be examined, to avoid unnecessary cordocentesis. 3) If KEL1 gene is not detected in the foetus, HDFN will not occur. 4/Foetal KEL1 genotyping may be performed in all mothers with anti-K and heterozygous father in our Department, after providing the material from the amniocethesis.