The series of experiments reported here investigated dimensions of children's sex stereotypes. The first study revealed that children were aware of sex stereotypes as early as 2 1/2 years of age. Furthermore, the tendency to categorize according to sex increased through their eighth year. The second study investigated whether sex stereotypes influenced children's evaluations of competent performance. It was found that, apparently, children base their evaluations of likely competence on the sex of the performer of sex-typed activities. The third study allowed children to express the strength of their beliefs in sex-typed evaluations of competence. Children's ratings of the competence of males' or females' performance on sex-typed activities revealed a clear bias toward sex-stereotyped performance. However, the children did not assume that the counterstereotypic performer would be totally incompetent, and ratings were closer to judgments of equal competence than to stereotyped extremes. Also collected were data on memory deficits for counterstereotypic portrayals; these revealed that children had considerable difficulty processing this type of information. Results of two additional studies indicated that discriminations based on sex stabilize by the time children reach the second grade and that children do not discriminate on the basis of sex when they make evaluations of individual performers. These results, additional findings, and implications of the findings are discussed. (RH)