The paper highlights the relation between positive distinctiveness and social discrimination as key concepts in Social Identity Theory. The often replicated finding of mere categorization leading to ingroup favouritism and outgroup discrimination plays a major role in supporting the view that discrimination is functional for a positive social identity. The paper confronts the mere categorization effect with recent findings which throw severe doubts on its robustness. Particularly the failure to extrapolate categorization effects to intergroup behaviour involving aversive stimuli (the positive–negative–asymmetry of social discrimination) lead to the plea for further specifications of SIT and its validity.