The ventromedial hypothalamus (VMLvl) has been shown to play a key role in aggression in male mice, but whether it plays a similar role in females remains controversial. Both aggression-inducing conditions and mating increased directly measured neural activity in oestrogen-expressing neurons in the VMLvl. In addition, VMLvl oestrogen-expressing neurons that were active during mating and aggressive behaviour were non-overlapping, suggesting that different subpopulations of these cells are involved in these two behaviours.