Healthcare policies regarding hematopoietic stem cell transplantation (HSCT) must address the need for the procedure as well as the availability of stem cell sources: bone marrow, peripheral blood, or umbilical cord blood (UCB). However, data with respect to the lifetime probability of undergoing HSCT are lacking. This study was undertaken to estimate the latter probability in the United States (U.S.), depending on age, sex, and race. We used data from the Center for International Blood and Marrow Transplant Research, the U.S. Surveillance, Epidemiology and End Results Program, and the U.S. Census Bureau and calculated probabilities as cumulative incidences. Several scenarios were considered: assuming current indications for autologous and allogeneic HSCT, assuming universal donor availability, and assuming broadening of HSCT use in hematologic malignancies. Incidences of diseases treated with HSCT and of HSCTs performed increase with age, rising strongly after age 40. Among individuals older than 40, incidences are higher for men than for women. The lifetime probabilities of undergoing HSCT range from 0.23% to 0.98% under the various scenarios. We conclude that, given current indications, the lifetime probability of undergoing autologous or allogeneic HSCT is much higher than previously reported by others and could rise even higher with increases in donor availability and HSCT applicability.