Sometimes researchers fail to meet their recruitment targets, and sometimes it is predicted that recruitment may prove difficult but it is not obvious what ethical latitude researchers have to boost participation by, for instance, paying participants to take part or by paying family doctors to recruit patients to participate. In this paper, we distinguish between payment, reimbursement and inducement. We look first at the ethics of paying research participants. We conclude that payment raises all kinds of ethical difficulties, but that reimbursement-whilst not completely unproblematic-is an ethical requirement. We then look at whether some inducement to participate is acceptable and conclude that it is. We continue by asking whether the same arguments can be applied to encouraging family doctors to recruit patients. We conclude that it is right for family doctors to be reimbursed for the costs of recruiting research participants and also argue that there are fewer problems with paying family doctors to recruit patients than there are with paying research participants. Given, however, that there is a fine line between reimbursement and payment, given the potential for conflicts of interests to arise, and given that even suspicion of such a conflict might undermine trust in doctors, systems of both payment and reimbursement need to be transparent.