This report reviews studies addressing the issue of the effect that carbohydrates have on affective behavior. The review begins with an overview of the physiologic and psychological mechanisms that have been proposed to explain a carbohydrate-induced behavioral effect. Attention is then devoted to studies that have investigated the mood-altering effect of carbohydrates on normal individuals, depressed individuals, obese individuals, and individuals with seasonal affective disorder and premenstrual syndrome. Throughout the report it is apparent that carbohydrate consumption is relevant for individuals experiencing symptoms of emotional distress, particularly symptoms indicative of depression, and that the individuals with depressive symptoms show a preference for sweet simple carbohydrates. Enduring questions permeating the diet-behavior field are delineated and future research directions are suggested.