AB - Gonadal steroids are major neuroregulators, and their actions have been proposed to underlie many of the sex differences in brain structure and function. Both basic and clinical studies suggest that these neuroregulatory effects of reproductive steroids are context dependent, with context including age, sex, environment/past experience, and genotype. This chapter focuses on the effects of gonadal steroids on brain function and behavior in women. First, background information is provided on the reproductive endocrine system in women, including the regulation of the hypothalamic-pituitary-ovarian axis, as well as the endocrinology of the menstrual cycle, pregnancy, the postpartum, and the menopause transition. Second, data will be discussed that demonstrate the role context plays in determining a differential response to gonadal steroids within the central nervous system. Third, evidence from neuroimaging and neuroendocrine studies in humans is described that demonstrate the important neuroregulatory effects of gonadal steroids on physiological systems mediating affective adaptation. Fourth, existing literature is reviewed regarding clinical characteristics and neurobiology of reproductive endocrine-related mood disorders. Finally, recent findings are discussed that identify sources of differential behavioral sensitivity in humans, including polymorphic genetic variants in the steroid signaling pathways and differences in steroid metabolism.