In this study we investigated the human leucocyte antigen-A (HLA-A), -B and DRB1 polymorphism of Native American population of Paraguay, the Guarani Indians. We found that the HLA variability consisted of 5 HLA-A, 7 HLA-B and 6 HLA-DRB1 groups of alleles and of several specific alleles (B*1504, B*3505, B*3912, B*4004, B*5104, DRB1*0411, DRB1*1413) common in other Native American populations. The comparison of the HLA polymorphism of the Guaranis from Paraguay with the «Mestizos» of Paraguay and the Spaniards showed that the «Mestizos» of Paraguay are genetically very distant from the Guarani Indians of Paraguay but much more close to the Spaniards. This can be explained, at least in part, by the history of the country. Our results are of importance in transplantation, in particular in the search for an unrelated donor for a Paraguayan patient requiring hematopoietic stem cell transplantation.