Increase in sex-role knowledge represents an early stage of the development of sex role stereotypes in children, which is followed by a decrease in the extent of sex-role discrimination. This process is related to the acquisition of classificatory skills. Groups of children aged 4-10 years were tested for their sex role stereotypes and classificatory skills. Sex role stereotypes were measured by having subjects assign 38 sex-linked traits, behaviors, and interests of children and adults to one of five categories ranging from extremely feminine to extremely masculine. Seven classification abilities were examined by a set of tasks that required subjects to attend to sex and age of human figure silhouettes. Data analyses of stereotype answers revealed a developmental sequence of an increase of stereotype knowledge accompanied by the tendency to group sex role characteristics into exclusive classes, males or females only. The acquisition of more flexible sex-role stereotypes conceptualizing sex role characteristics as partially common to both sex groups was also noted. The developmental change in sex role stereotyping was closely related to the level of classification ability. The findings support a cognitive developmental theory of sex role development. (Author/DWH)