This article begins with the observation that most contemporary theories of justice pay no attention to the concept of need. And, as my main thesis, I shall argue that this is not correct. First of all (I) I shall explain the reasons for this theoretical deficit and I shall strictly distinguish (II) the concept of “need” from other concepts, such as “wish” and “drive”, which are routinely interpreted as its synonyms. Then (III) I shall offer a definition of need which is based on a complex conception of human personality. I shall introduce an enumeration of the various levels of the person by which various categories of need correspond with various objects. In the next step (IV) I shall tackle the question of whether in some regard it is necessary to treat needs as reasons for conduct. In this context I shall briefly present a historico-naturalistic account which aims to provide a grounding for judgements about questions of human needs. (V). Finally I shall deal with the social dimension of human needs and I will put forward reasons for the view that a theory of social justice should deal with the concept of need as its main theme (VI).