Proposals for increasing organ donation are often rejected as incompatible with altruistic motivation on the part of donors. This paper questions, on conceptual grounds, whether most organ donors really are altruistic. If we distinguish between altruism and solidarity – a more restricted form of other-concern, limited to members of a particular group – then most organ donors exhibit solidarity, rather than altruism. If organ donation really must be altruistic, then we have reasons to worry about the motives of existing donors. However, I argue that altruism is not necessary, because organ donation supplies important goods, whatever the motivation, and we can reject certain dubious motivations, such as financial profit, without insisting on altruism. Once solidaristic donation is accepted, certain reforms for increasing donation rates seem permissible. This paper considers two proposals. Firstly, it has been suggested that registered donors should receive priority for transplants. Whil