The dermatoglyphic pattern of dermal ridges that constitutes the human fingerprint is complete by the 16th foetal week and its development is thought to be influenced by prenatal hormones. Finger ridge count (FRC) is asymmetrical with the majority having more ridges on the finger tips of the right hand (R >) while the minority have more on the left (L >). In adults, the R > condition has been associated with male-typical, and the L > condition with female-typical, performance on sexually dimorphic tasks. Here we report that 60 prepubescent children showed the same sex difference and the same relationship as adults between FRC and task performance: girls and L > children performed a female-favouring task better while boys and R > children performed a male-favouring task better. This finding indicates that these sex-related task performance differences are not dependent on the activational effects of adult gonadal steroids. The implications of these findings for prenatal influences on neuropsychological development are discussed.