The consolidation of organ transplants as routine medical therapy made necessary to build institutions to solve problems of organ procurement and organ allocation. These institutions, though similar in some respects to economic institutions that organize the collective procurement of scarce resources, have distinctive attributes. In this paper we analyze the architectonic structure of the institutions that regulate organ procurement and their underlying logic. Since human organs for transplants are cultural constructions that carry both moral and symbolic value, the institutions of organ procurement are strongly shaped by value rationality. Value rationality explains the choice of gift giving as the institutional mode to regulate organ procurement, instead of market or state procurement. Value rationality also explains the trend toward institutional isomorphism across countries within the field of organ transplants. Finally, I present an outline of the Spanish case, in order to show the possibility of successful microinstitucional innovation in the context of institutional isomorphism.