John Rawls developed principles of justice to guide the fair allocation of resources in a society. However, his principles did not take into consideration a society’s differing health needs. Norman Daniels attempted to extend Rawlsian principles of justice to apply to the allocation of health resources. In Just Health, Daniels argued that, under certain circumstances, an age-based allocation of health resources can be prudent. He proposed the Prudential Lifespan Account (PLA) to defend age-rationing against claims that it would lead to favoring one age-group over another. In this paper, I analyze Daniels’s PLA and argue that societal aging poses a significant threat to its effectiveness. I then examine and critique alternate theories to extend Rawlsian principles of justice to account for health, specifically those proposed by Dennis McKerlie and Hugh Lazenby.