The present investigation studied the effect of the sex typed labelling of tasks on children's performance. The children were selected from the 1st, 3rd and 6th forms. To investigate whether the sex appropriate labelling of the task had a direct influence on performance, the same measure of performance - a perceptual motor task - was used across all conditions. The task was labelled either as Needlework (female appropriate) or Electronics (male appropriate). Two main dimensions were investigated. Firstly, the effect of direct labelling of a task as sex appropriate or inappropriate. Secondly, the effect of the instruction to role enact a person competent at the task. In the second study, the role enactment procedure required the children to enact a same age peer whose sex was congruent with the sex typing.of the task. Results of both studies indicated that children perform better at tasks labelled as sex appropriate compared to sex inappropriate. Under the role enactment conditions in both studies, children performed at a higher level than under conventional testing procedures. However, whilst in the role enactment procedure there was no difference in the performance of girls between sex appropriate and sex inappropriate labelled tasks, boys perform better at sex appropriate tasks in both studies. Two measures of sex role stereotyping were used in the investigation. The Rosenkrantz, et al (1968) sex role questionnaire established that the sex role stereotyping of the sixth form sample was similar to a British adult sample. A measure of sex role stereotyping (S. Measure), was developed on a comparable sample of children to the sample selected in the present study. Although the direct relationship between sex role stereotyping and task performance was not established, results suggested the more rigid sex role stereotyping of boys. The third study examined further the effects of sex role enactment on children's performance at tasks. Children were selected from the 3rd and 6th forms. Two tasks were employed, differing on the dimensions of convergence-divergence and sex typing. The tasks were a mechanical reasoning test (D.A.T., 1973) and the Uses of Objects test (Hudson, 1968). Results indicated that under the conventional administrative procedures, boys scored better than girls on the mechanical reasoning test, whereas girls scored better than boys on the Uses of Objects Test. However, the effect of opposite sex role enactment differ- , ed for the 3rd and 6th formers. At the 3rd form level, boys , and girls scores reflected differences in performance according to sex typed dimensions. However, at the sixth form level, girls exhibited a slight but non-significant increase in mechanical reasoning scores and decrease in Uses of Objects scores, while boys'scores significantly decreased on both tasks. The results are interpreted in terms of the increased salience of sex-appropriateness of tasks at adolescence. Further, the results of the measure of sex role stereotyping, B.S.R.I (Bern, 1974) from which,due to sample size,only limited conclusions may be drawn, confirm the results derived from the S Measures of sex role'stereotyping of the stricter adherence of boys to the masculine stereotype