The ventromedial nucleus of the hypothalamus (VMH) is a sexually differentiated area of the rodent brain, with a larger volume in males than females. We previously found a sex difference in neuronal number in the mouse VMH, and also found that circulating testosterone in adulthood regulates volume in the region, specifically in the ventrolateral and dorsomedial subregions. The current study uses gonadally intact male and female adult mice to examine VMH subregion volume, astrocyte number, and astrocyte complexity. Brains were stained for GFAP and counterstained with Harris Hematoxylin, the VMH was traced at low magnification, and an unbiased sample of astrocytes were counted and traced at high magnification. The results confirmed a sex difference in overall VMH volume with males (mean male volume = 1.6 ± .066 x 108 um3) having larger volume than females (mean female volume = 1.4 ± .044 x 108 um3). More specifically, we find that the dorsomedial and ventrolateral subregions again accounted for this sex difference in volume. We now report that males have more VMH astrocytes (mean male number = 13.7 ± .414 x 103, mean female number = 9.1 ± .26 x 103) and more complex astrocytes (longer primary branches and more branch endings) than females. We are currently examining whether these results differ across VMH subregions. These results show that in addition to sex differences in volume and neuron number in the VMH, there are also sex differences in astrocyte number and complexity. These sex differences in neural morphology may underlie sex differences in behaviors associated with the VMH, including aggression, maternal behavior and sexual receptivity.