Mammals engage in a number of opponent behaviors that contribute to survival. In order to do so successfully, they must be able to flexibly switch from one behavior to another. The relationship between sex and fear is one such example of opponent behaviors. However, the neural circuitry controlling the relationship between sex and fear has not been systematically investigated. Previous findings have established a role for the medial preotic area (MPO) in the control of sexual behavior in the mammalian brain. However, the question of whether the MPO also contributes to fear has never been examined. In pilot studies in our laboratory, we have identified genetically separable populations of neurons in MPO that control fear and mating in mice. By combining optogenetics, chemogenetics, immunohistochemistry, behavioral testing and in vivo imaging, we aim to further isolate, characterize and control these separate neuronal populations. Identification of the neural circuits underlying sex and fear in the brain will contribute towards our understanding of how these circuits interact to produce adaptive behavior, as well as the conditions under which the relationship between sex and fear can become maladaptive. Furthermore, these findings identify for the first time a role for the MPO in fear.