Cortical complexity, a measure that quantifies the spatial frequency of gyrification and fissuration of the brain surface, has not been thoroughly characterized with respect to gender differences in the human brain. Using a new three-dimensional (3D) analytic technique with magnetic resonance imaging, we found greater gyrification in women than men in frontal and parietal regions. Increased complexity implies more cortical surface area, which may offset gender differences in brain volume and account for behavioral gender differences.