This article explores the problem of justice between age-groups. Specifically, it presents a challenge to a leading theory in this field, Norman Daniels' Prudential Lifespan Account. The challenge relates to a key assumption that underlies this theory, namely the assumption that all individuals live complete lives of equal length. Having identified the roles that this assumption plays, the article argues that the justifications Daniels offers for it are unsatisfactory and that this threatens the foundation of his position, undermining his claim (...) that ‘the fact that we all age’ makes age a special problem of distributive justice. This shows that the problem of justice between age-groups is not special in the way Daniels proposes; rather it involves the same irreducibly interpersonal distributive decisions as other problems of justice. The consequences of this argument are several-fold. Most importantly, it shows that the Rawlsian account of justice to which Daniels hopes to attach his theory to requires significantly greater benefits to be conferred on those in earlier age-groups relative to those in later age-group, not a distribution similar to simultaneous equality as Daniels proposes. (shrink)