Hematopoietic stem cell transplantation is the most effective treatment for acute leukemia, severe aplastic anemia, and some hereditary hematological disorders. The principal source of stem cells in this procedure are bone marrow and peripheral blood cells. In recent years, the transplantation outcome has significantly improved. The availability of the donor no longer poses a problem, as transplantation has been performed routinely from related, unrelated, and haploidentical donors. A high success rate has been reported in elderly patients transplanted with reduced-intensity conditioning. Improved patient care has decreased toxicity and mortality after treatment. This article gives an overview of the 40-year history of the Zagreb transplant program. It also discusses the use of hematopoietic stem cell transplantation in various hematological disorders, with a special emphasis on the publications by the Zagreb transplant team.