Previous social categorization research has tended to treat prototypicality (the degree to which a stimulus is representative of a category) as a fixed stimulus property. In contrast, self-categorization theory sees prototypicality as an aspect of the categorization process that is dependent on features of the social context within which categorization takes place. To test this view two experiments (Ns = 256, 73) examined the perceived representativeness of extreme and moderate members of the same target outgroup in conditions which manipulated the salience of intergroup division. As predicted, the extremist was seen to be relatively more representative of the outgroup than the moderate to the extent that intergroup differences were salient. In Experiment 1 the extremist's message was also seen to be less important in low salience conditions and in Experiment 2 shifts in prototypicality were associated with changes in the evaluation of individual targets. Implications for the analysis of social categorization and stereotyping are discussed.