Prenatal exposure to testosterone is thought to promote the development of the right-hemisphere and increase the incidence of sinistrality. A direct test of this hypothesis has previously been problematic because of the difficulty of indirectly assessing prenatal sex steroid exposure. Evidence now suggests that the ratio between the length of the second and fourth digits (2D:4D) is related to prenatal testosterone exposure. We tested whether digit ratio is related to the degree of hand skill such that low 2D:4D (indicating high levels of testosterone in utero) may be correlated with enhanced left-hand performance. In right-handed children, high 2D:4D correlated with improved right-hand skill and low 2D:4D correlated with enhanced left-hand skill. Correlations were found to be similar for girls and for boys. Since low 2D:4D has been previously reported to be associated with faster left-hand speed compared to right in Afro-Caribbean children with very low mean 2D:4D, the present finding in a Caucasian population with high mean 2D:4D suggests that a tendency of improved left-hand performance due to prenatal testosterone may be found across ethnic groups. (C) 2004 Elsevier B.V. All rights reserved.