Blood stem cell transplants can be life-saving for some patients, but the chances of finding a matching donor are small unless a large number of potential donors are evaluated. Many nations maintain large registries of potential donors who have offered to donate stem cells if they are the best available match for a patient needing a transplant. An alternative source of stem cells, umbilical cord blood, is stored in banks. Everyone faces a small probability of needing a transplant which will increase their likelihood of survival. The registries and cord blood banks are thus an interesting example of a pure public good with widely dispersed benefits. This paper explores the gains in survival probability that arise from increased registry and bank sizes and uses value of statistical life methods to estimate benefits and compare them to costs. Our results suggest that for the United States and for the world as a whole, the sum of marginal benefits of an increase in either the adult registry or the cord blood bank exceeds marginal costs. However, marginal benefit-cost ratios for the adult registry are much greater than those for the cord blood banks, which suggests that to the extent that these two sources of life saving compete for public funds it may be preferable to prioritize expansion of the adult registry over cord blood banks.