An HLA-matched sibling remains the optimal donor for most patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Marked declines in total fertility rates in Canada over the past 50 years will lead to increasing numbers of patients without sibling donors well into the future. We retrieved transplantation data from a Canadian center and the Canadian Blood and Marrow Transplant Group and total fertility data from the United Nations Department of Economic and Social Affairs. The mean age of adults with acute myelogenous leukemia (AML), who underwent transplantation at The Ottawa Hospital between 1995 and 2004, was 41 +/- 12 years (n = 87). The chance of finding 1 or more HLA-matched sibling donors for a patient with AML treated in 2002 is reflected by the total fertility rate in 1961 (average birth year for patients and sibling donors). The sibling rate for 1961 is the total fertility rate-1.0, or 2.68. The chance of having 1 or more HLA-matched sibling is 53.7% (1-chances of no matched sibling, or 1 - 0.75(2.68)). In 2009, the chance of identifying a matched sibling is only 37.1%, because of declining total fertility rates. Following this trend, this chance will be 24.6% in 2014 and 16.6% in 2024. Greater reliance on alternative donors, such as umbilical cord blood (UCB) and HLA-mismatched donors, can be anticipated. The issue of declining fertility rates appears to be regional, and the impact on transplantation will be more pronounced in Canada than in other developed nations.