Recent shortages in the supply of blood donations have renewed the interest in how blood donations can be increased temporarily. We survey the evidence on the role of financial and other incentives in eliciting blood donations among donors who are normally willing to donate pro bono. We present the predictions from different empirical/psychological-based theories, with some predicting that incentives are effective while others predict that incentives may undermine prosocial motivation. The evidence suggests that incentives work relatively well in settings in which donors are relatively anonymous, but evidence indicates also that when image concerns become important, incentives may be counterproductive as donors do not want to be seen as greedy.