The progress in HLA research achieved in the last decade has been extremely beneficial for understanding of the human genome structure, evolution of human beings and the association between HLA and complex related factors like immune responsiveness and patomechanism of some diseases. It was also found that some HLA specificities may bear a witness not only to a susceptibility to some diseases but also may reflect the ability of the host to mount immune responsiveness. All these achievements enabled successful clinical application of haematopoietic stem cells transplantation. Nowadays, it is apparent that the perfect matching at allele level of HLA specificities constitute the most important factor affecting surviving of patients transplanted from unrelated donors. This is also shown in this volume. To secure reliability of HLA typing , DNA techniques should be implemented and laboratories should comply with requirements expressed by European Federation for Immunogenetics (EFI) and American Society for Histocompatibility and Immunogenetics (ASHI). HLA typing is a complex procedure which should involve internal and external quality controls. Haematopoietic stem cell transplantation may be the best example of introducing modern technologies and very active translation of basic research in the fields of genetics and cell biology into the clinic. Even more impressive is international collaboration in searching for the best possible donor wherever in the world it might be. More than 8 million donors are registered world-wide. There is an ongoing interest in improving the international co-operation in order to secure the best donors for recipients. These chapters are of special interest as the co-operation for donors selection for HSCT is an activity across the oceans.