This chapter analyzes the ethics of killing animals when animals are assumed to be unable to form desires about the future and to lack a conception of themselves through time. Even if their mental abilities are so limited, they can still be harmed by being killed, and so inducing their deaths will require justification. My argument employs the notion of a time-relative interest, which is the interest an entity has in continuing to live. This interest is shaped by two factors: the gain or loss of future well-being, and the amount of psychological continuity between the entity now and in the future (when its well-being improves or declines). After outlining the time-relative interest account I note how it differs from another influential argument that takes future well-being into account, Don Marquis’ argument against abortion. I then defend the time-relative interest account from the criticism that it fails to grant weight to interests a deceased individual would have come to posses had he or she not died. Finally, I show why my view is consistent with a universal legal ban on infanticide.