Differences in the number of hematopoietic SCTs (HSCT), in transplant rates, in indications and in techniques between countries have been reported. They were attributed mainly to differences in the economic situation of the countries or to differences in prevalences of the disease. On the basis of the results of the annual activity survey on HSCT of the European Blood and Marrow Transplantation (EBMT), we have analyzed the factors associated with differences between more than 600 teams participating from more than 40 countries over a time span of 15 years. The results show a more complex situation. The gross national income per capita, number of transplant teams per 10 million inhabitants or per 10,000 km2, team size and team experience all impact on transplant activity. Furthermore, hitherto unknown factors must add to the decisions to perform or not to perform HSCT. These data illustrate that more research is needed to understand the mechanism of HSCT activity and to enable health-care agencies to provide the necessary infrastructure.