Although it is well recognized that individual people and other social objects are multiply categorizable, common conceptions of mental representation in social psychology do not easily allow for this property. In this chapter two more flexible types of model that treat representations as transient states rather than as static things are reviewed: exemplar and distributed representations. Both of these can accommodate multiple categorizations. If such types of representation are assumed, questions naturally arise about the factors that influence which of many available categorizations will be used. To complement the emphasis within the social identity tradition (Tajfel & Turner, 1979; Turner, Hogg, Oakes, Reicher, & Wetherell, 1987) on the social context as a determinant (see McGarty, this volume), two factors involving the perceiver are suggested as potentially important, based on prior research. The perceiver’s practice or experience in categorizing a particular individual in one way or another, as well as the strength of the perceiver’s attitudes toward potential categories, ought to affect the likelihood of categorizing a person in one way or another.