There is a large body of accumulated evidence from behavioral and neuroimaging studies regarding how and where in the brain we represent basic numerical information. A number of these studies have considered how numerical representations may differ between individuals according to their age or level of mathematical ability, but one issue rarely considered is whether the representational acuity or automaticity of using numerical representations differs between the sexes. We report 4 studies that suggest that male participants show a stronger influence of the spatial representation of number as revealed through the spatial numerical association of response codes (SNARC) effect, through the numerical distance effect (NDE), and through number-line estimations. Evidence for a sex difference in processing number was present for parity decisions (Experiment 1), color decisions (Experiment 2), number-line estimations (Experiment 3), and magnitude decisions (Experiment 4). We argue that this pattern of results reflects a sex difference in either the acuity of representation or reliance upon spatial representations of number, and that this difference may arise due to differences in the parietal lobes of men and women. (Contains 3 figures and 1 table.)