The authors describe the first successful case of transplantation of haematopoietic stem cells in a patient with severe congenital immunodeficiency-the syndrome of deficiency of leukocytary integrins (LAD), leukocyte adhesion deficiency) in the Czech Republic and, at the same time, the first successful transplantation of umbilical blood in this disease in the world. The six-year boy was completely cured by the transplantation of haematopoietic stem cells contained in umbilical blood sampled during delivery of his healthy brother with identical HLA system. The pretransplantation myeloablative preparation was performed by a combination of busulfan, cyclophosphamide and etoposide. The relatively uncomplicated posttransplantation course was secured by preventive administration of antibiotics and immunoglobulins. The reattachment of the stem cells, estimated from the peripheral blood picture, occurred 25 days after the transplantation, the success of the intervention was confirmed by reaching physiological values of originally null expression of integrins on leukocytes of the patient 30 days after the transplantation. The transplantation of umbilical blood is a very promising therapeutic method especially in children with leukemia, congenital severe immunodeficiencies o inborn errors of metabolism.