Penile erection occurs in response to tactile, visual, and imaginative stimuli in humans. In animals olfactory and auditory cues are particularly important. The participation of multiple sites with the brain and spinal cord, and coordination of somatic and autonomic pathways make sexual behavior in general, and erection in particular, vulnerable to neurologic injury and disease. Sites within the brain and spinal cord act in concert to process, coordinate, then distribute the neural inputs necessary for sexual behavior including erection. Activation of neurons in some of these regions either pharmacologically or by electrical stimulation has been associated with penile tumescence. This review will provide a geographic framework for understanding the neuroanatomical basis of penile erection based primarily on animal data. Following discussion of the anatomical substrates, a clinical correlation is then provided to confirm and reinforce these experimental observations.