Certain groups of HLA gene alleles play an important role in emergence of acquired aplastic anemia (AAA). We studied HLA antigens in Slavic children with AAA of different clinical forms, severity, and response to immunosuppressive therapy (IST). The study was carried out in 147 children With AAA. The reference group was formed from 1700 specimens of umbilical blood from healthy newborns. HLA genotyping showed that DRB1*15 and B*51 were common markers of liability to idiopathic aplastic anemia for boys from the age of 14 years and girls aged under 14 years; characteristic markers were DQB1*06 for girls aged under 14 years and B*08, B*40, DRB1*03 for boys aged under 14 years. A common marker of liability to extremely severe AAA in boys and to severe AAA, including the disease sensitive to combined IST, was HLA-DRB1*15; characteristic markers of liability to extremely severe AAA in boys were B*08, B*14, and DRB1*03. These results suggested a novel view on the available models of AAA pathogenesis.