The argument that scarce health care resources should be distributed so that patients in 'need' are given priority for treatment is rarely contested. In this paper, we argue that if need is to play a significant role in distributive decisions it is crucial that what is meant by need can be precisely articulated. Following a discussion of the general features of health care need, we propose three principal interpretations of need, each of which focuses on separate intuitions. Although this account may not be a completely exhaustive reflection of what people mean when they refer to need, the three interpretations provide a starting-point for further debate of what the concept means in its specific application. We discuss combined interpretations, the meaning of grading needs, and compare needs-based priority setting to social welfare maximisation.