The present work suggests that self-control relies on glucose as a limited energy source. Laboratory tests of self-control (i.e., the Stroop task, thought suppression, emotion regulation, attention control) and of social behaviors (i.e., helping behavior, coping with thoughts of death, stifling prejudice during an interracial interaction) showed that (a) acts of self-control reduced blood glucose levels, (b) low levels of blood glucose after an initial self-control task predicted poor performance on a subsequent self-control task, and (c) initial acts of self-control impaired performance on subsequent self-control tasks, but consuming a glucose drink eliminated these impairments. Self-control requires a certain amount of glucose to operate unimpaired. A single act of self-control causes glucose to drop below optimal levels, thereby impairing subsequent attempts at self-control.Keywords: self-regulation, glucose, attention, emotion regulation, prejudice Self-control (or self-regulation) is the ability to control or override one's thoughts, emotions, urges, and behavior. Self-control allows for the flexibility necessary for successful goal attainment, and it greatly facilitates adherence to morals, laws, social norms, and other rules and regulations. As such, it is one of the most important and beneficial processes in the human personality structure. A burgeoning body of evidence has linked good self-control to a broad range of desirable outcomes, including healthier interpersonal relationships, greater popularity, better mental health, more effective coping skills, reduced aggression, and superior academic performance, as well as less susceptibility to drug and alcohol abuse, criminality, and eating disorders (DeWall,