Numerous studies suggest that premenstrual syndrome (PMS) may be linked to impaired self-control since many of the symptoms of PMS are indicative of impaired self-control. Evidence links PMS to increased difficulty controlling emotions, attention, and fine motor movements; increased intake of alcohol, drugs, nicotine, caffeine, and food; impaired work performance, and increased stress, aggression, criminal behavior, interpersonal conflicts, and passivity. Empirical research demonstrates that self-control is metabolically expensive and, as such, can be impaired when metabolic energy (i.e., glucose) is low or processed ineffectively. The expression of PMS is tightly linked to the luteal phase of the menstrual cycle, a time in which considerable metabolic energy is allocated to the ovaries. This increased ovarian metabolic demand could, therefore, divert energy away from, and thereby impair, other processes during this phase of the menstrual cycle. Here, we propose a novel theory in which PMS symptoms are partly attributable to the diversion of metabolic energy to the ovaries and away from processes that benefit self-control.Premenstrual syndrome (PMS) and related conditions including late luteal phase dysphoric disorder, premenstrual dysphoric disorder, and premenstrual tension are associated with negative physical (e.g., bloating) and mental symptoms (e.g., mood swings) that occur during the late luteal phase of the menstrual cycle (Ivey & Bardwick, 1968). Women who suffer from PMS often show unpleasant symptoms ranging from societal ills (e.g., crime) to reduced personal fulfillment (e.g., interpersonal problems). Although the symptomatology is well documented, the mechanism underlying PMS is poorly understood. Here, we propose a novel theory of PMS that is based on the observation that PMS symptoms occur during the most metabolically expensive phase of the menstrual cycle (i.e., the luteal phase) and on the assumption that self-control depends on energy resources that may be atypically low during this phase of the cycle. Thus, it is possible that the increased metabolic demands of the body during the luteal phase may deplete the body's common energy stores and thereby impair self-control, insofar as self-control relies on the same energy and is often curtailed when energy has been depleted. This impaired selfcontrol may then contribute to the symptomatology of PMS.In support of our metabolic theory of PMS, we first review evidence that the use of metabolic energy is limited and that one set of biological processes can divert energy away from other processes. We then provide evidence that metabolic demands increase during the luteal phase and this, in a subset of women, hampers self-control due to an inadequate store of metabolic energy (i.e., glucose). Instead of asserting that the premenstrual phase gives rise to antisocial or unpleasant impulses, we suggest that the impulses remain about the same, but the weakening of self-control allows them greater than normal opportunity to be expressed overtly. Based on th...