Libido is a comprehensive and yet elusive word that indicates basic human mental states--and their biological counterparts--involved in the beginning of sexual behavior. It has three main roots: biological, motivational-affective and cognitive. All these dimensions may be variably affected in the post menopause, contributing to a progressive decrease of sexual drive that parallels the process of aging. Loss of estrogens and, specifically, of androgens deprives female libido of major biological fuel. The effect of this loss is pervading, affecting the central nervous system, the sensory organs that are the major windows to environmental sexual stimuli and the quality of sexual response, central, peripheral non-genital and genital. Prolactin increase may further inhibit libido. Arousal disorders, dyspareunia, orgasmic difficulties, dissatisfaction, both physical and emotional, may contribute to a secondary loss of libido. Depression, anxiety and chronic stress, may interfere with central and peripheral pathways of the sexual response, reducing the quality of sexual function mostly in its motivational root. Relational conflicts and/or marital delusions and partner-specific problems, erectile deficit first, may contribute to the fading of sexual drive in the post-menopausal years. Well tailored HRT, including androgens in selected cases, may reduce the biological causes of loss of libido. A comprehensive treatment requires a balanced evaluation between biological and psychodynamic factors.