Based on observations under laboratory conditions of over 300 couples, Masters and Johnson identified four discrete phases of the human sexual response as arousal (excitement), plateau, orgasm and satisfaction. This sequence was subsequently modified to include the phase of sexual drive: Kaplan proposed a triphasic response model, each phase with a distinct underlying neurophysiological basis. Libido is defined as the biological need for sexual activity (sex drive) and depends upon hypothalamic and temporal lobe functioning. This chapter outlines the roles of the subcortical and cortical regions, spinal connections and peripheral innervation involved in the phases of the human sexual cycle, with reference to the experimental animal literature and mention of the dysfunctions that can result from neurological disease at each level. Findings from recent functional imaging experiments are discussed in the context of the role of the cortical regions in human neurological control of sexual function.