This article describes the ways in which arousal and sexual urges in women and men reflect sex differences in the links between brain responses and genital changes. Boys are more sexually motivated from puberty on, whereas girls tend to seek emotional connections as a precursor to sexual contact. Although feelings and thoughts are important for both sexes, women are not always psychologically aroused by genital vasocongestion, while the opposite tends to pertain to men. Lack of subjective arousal commonly leads to loss of sexual interest in women: negative emotions in the current relationship are often involved. For men, the causes of sexual withdrawal are more variable, and childhood family dynamics are a frequent, but unconscious, factor. The role of the neuropeptides oxytocin and vasopressin, synthesised from oestrogen and testosterone respectively, is described as a biological underpinning for some observed gender differences. Oxytocin is released at orgasm by both women and men and promotes sexual pleasure and emotional bonding. Vasopressin, secreted during the male arousal phase, is linked to men’s drive for sexual expression. This peptide may have the opposite effect on women and impair arousal and motivation due to the link between vasopressin release and aggression. Psychological treatment needs to explore the meaning of lack of sexual motivation for each person, and to address individual and couple issues. An integrated psychosexual model combining behavioural and psychodynamic approaches can alter feelings and relational patterns, and facilitate the return of sexual desire between partners in a committed relationship.