According to self-categorization theory (Oakes, Haslam, & Turner, 1994), stereotypes vary to reflect variations in the comparative context within which they are formed. In this study we explore stereotype variability in a sample of 5- and 7-year-old children. Participants described a specific out-group, and then described the in-group (that is ‘boys’ or ‘girls’, depending on the sex of the participant). Description was provided by judging the proportion of group members to whom each trait from a list was seen as applicable. There were two experimental conditions: in the first condition the outgroup was represented by adult ‘men’ if participants were boys, or by adult ‘women’ if participants were girls. In the second condition the out-group was represented by ‘girls’, if participants were boys, or by ‘boys’, if participants were girls. Descriptions of the in-group were found to differ significantly with changes in the frame of reference amongst both 5- and 7-year-olds, though more for boys than girls. Overall, such findings challenge the widely held view that stereotypes are endemically stable cognitive structures.