Sex hormones exert differential effects on a variety of sensitive tissues like the reproductive tract, gonads, liver, bone and adipose tissue, among others. In the brain, sex hormones act as neuroactive steroids regulating the function of neuroendocrine diencephalic structures like the hypothalamus. In addition, steroids can exert physiological effects upon cortical, limbic and midbrain structures, influencing different behaviors such as memory, learning, mood and reward. In the last three decades, the role of sex hormones on monoamine neurotransmitters in extra-hypothalamic areas related to motivated behaviors, learning and locomotion has been the focus of much research. The purpose of this thematic issue is to present the state of art concerning the effects of sex hormones on the neurochemical regulation of dopaminergic midbrain areas involved in neurobiological and pathological processes, such as addiction to drugs of abuse. We also discuss evidence of how neonatal exposure to sex hormones or endocrine disrupting chemicals can produce long-term changes on the neurochemical regulation of dopaminergic neurons in the limbic and midbrain areas.