 This entry does not provide a full account of allocation principles for organs. Rather, it aims to do three specific things. First, it explains some of the features of allocation of organs that need to be taken into account when applying basic principles. This section draws to the attention of philosophers the real-world complexity of applying abstract principles of allocation. Second, it discusses the problems of responsibility for condition and social value. These problems are both ethically interesting and, while not unique to organ allocation, are more poignant than for other scarce resources because they often cannot be avoided just by making more money available. Third, it describes some transplantation-specific cases of the interaction between allocation rules and the number of organs retrieved for transplantation. These cases raise doubts about the coherence of some actually existing allocation practices.