An association between hormones and psychiatric disorders has been long recognized, but it is only in the past few decades that we have reached an understanding of the mechanisms underlying this association. A full account of the myriad ways in which the various endocrine systems influence neurobehavioral function would be beyond the scope of a single chapter. We will therefore focus on examples of promising research directions in this area: namely, how the stress and reproductive hormone axes contribute to the pathoetiology of psychiatric conditions, in particular mood and anxiety disorders.