Night eating syndrome (NES), an eating disorder that has been linked to obesity, was first described in 1955. It occurs when the normally synchronous patterns of energy intake and sleep become disrupted; the result of this dysynchrony is a relative phase delay between the disordered eating patterns and the normal sleep-wake cycles. Although specific criteria for NES have not yet been validated, the characteristic associated behaviors are evening hyperphagia, morning anorexia, and insomnia. This article reviews NES prevalence, behavioral and neurohormonal manifestations of this disorder, criteria for its differential diagnosis, and current treatment options.