BACKGROUND Two European centres report on human leukocyte antigen (HLA) typing of preimplantation embryos for haematopoietic stem cell (HSC) transplantation: 'UZ Brussel' in Brussels and 'Genoma' in Rome. Both centres have 6 years' experience with technical and clinical aspects of this type of genetic analysis on single blastomeres. METHODS Both centres apply a similar technique for preimplantation HLA typing using short tandem repeats linked to the HLA locus in multiplex PCR for haplotyping. RESULTS At present, a conclusive HLA diagnosis could be assured in 92.8% and 90.3% of the embryos at UZ Brussel and at Genoma, respectively. The implantation rates were 32.4% and 28.2%, respectively, and the birth rates per cycle were 9.4% and 18.6%, respectively. The HLA programme at UZ Brussel and at Genoma resulted in the birth of 9 babies and 3 successful HSC transplantations, and 42 babies and 7 successful HSC transplantations, respectively, so far. CONCLUSIONS Drastic embryo selection for preimplantation HLA typing (in theory 1/4 for HLA, 1/8 for HLA in combination with sexing for X-linked recessive diseases, 3/16 for HLA in combination with autosomal recessive disorders) resulted overall in the birth of 51 babies (15.9% live birth rate per started cycle) in two European centres.