The background and development of motivational hypotheses in social identity theory are examined, revealing two general motives for intergroup discrimination: a desire for cognitive coherence, or good structure; and a need for positive self-esteem. The latter (self-esteem hypothesis: SEH) has received most attention. Both the theoretical and empirical bases of the SEH are largely rooted in research using the minimal group paradigm. However, it remains unclear whether self-esteem is to be considered primarily as a cause or an effect of discrimination. When real social groups are considered the SEH appears to provide only a partial explanation, and a variety of more or less powerful alternative social motives may underlie discriminatory behaviour. We explore some social-structural, individual and interpersonal limits to the SEH, and we call for an awareness of these motives and a re-examination of the good-structure thesis. The SEH, as it stands, provides only a partial contribution to our understanding of the relationship between social identity and discriminatory intergroup behaviour.