Samuel J. Kerstein develops a new, broadly Kantian account of the ethical issues that arise when a person treats another merely as a means, that is, 'just uses' the other and thereby acts wrongly. He takes his inspiration from Immanuel Kant's 'Formula of Humanity', which commands that we treat persons never merely as means but always as ends in themselves, and then develops the ideas suggested by the Formula into clear moral principles. Kerstein questions the plausibility of an orthodox Kantian account of the dignity of persons, before going on to develop a new, detailed account of his own. Kerstein's second main goal is to show how the Kantian principles he develops shed light on pressing issues in bioethics. He investigates how, morally speaking, scarce resources such as flu vaccine ought to be distributed--and he argues that allocating such resources in order to maximize benefits can be inconsistent with respecting persons' dignity. The book explores the morality of regulated markets in organs, and contends that in many contexts, buying organs from live 'donors' fails to honour their dignity. Finally, it probes the ethics of conducting research on 'anonymized' biological samples, and of conducting placebo-controlled pharmaceutical trials in developing countries. How to Treat Persons champions the view that even if an agent gets another's voluntary, informed consent to use parts of his body for transplantation or medical research, she might nevertheless be treating him merely as a means or failing to respect his dignity.