Analysis of over 2,000 brain scans revealed evidence of highly reproducible sex differences in the volume of different regions of the brain. On average, females had greater cortical volume in the medial and lateral prefrontal cortex, orbitofrontal cortex, superior temporal cortex, and lateral parietal cortex. Males had increased volume in the ventral temporal and occipital brain regions. Gene expression data suggest the potential role of sex chromosomes that contribute to the differences.