This essay supposes that the question of what treatment of animals is morally acceptable cannot be decided in any straightforward way by appeals to 'equal consideration of interests' or to animal rights. Instead it seeks to survey a variety of proposals as to how we ought to adjudicate interspecific conflicts of interests - proposals that are both 'speciesist' and 'non-speciesist' in nature. In the end one proposal is defended as the most reasonable one, and is claimed to provide a partial (...) basis for developing an adequate theory of interspecific justice. In the course of this argument the challenge posed by radical critics of current treatment of animals (e.g. Tom Regan and Peter Singer) is considered. The schema of a theory developed here partly supports and partly conflicts with positions they have defended. Regarding the latter point it proposes a non-anthropocentric basis for discounting the interests of sentient animals. (shrink)