Night eating syndrome (NES) is an eating disorder characterised by the clinical features of morning anorexia, evening hyperphagia, and insomnia with awakenings followed by nocturnal food ingestion. The core clinical feature appears to be a delay in the circadian timing of food intake. Energy intake is reduced in the first half of the day and greatly increased in the second half, such that sleep is disrupted in the service of food intake. The syndrome can be distinguished from bulimia nervosa and binge eating disorder by the lack of associated compensatory behaviours, the timing of food intake and the fact that the food ingestions are small, amounting to repeated snacks rather than true binges. NES also differs from sleep-related eating disorder by the presence of full awareness, as opposed to parasomnic nocturnal ingestions. NES is of importance clinically because of its association with obesity. Its prevalence rises with increasing weight, and about half of those diagnosed with it report a normal weight status before the onset of the syndrome. The recognition and effective treatment of NES may be an increasingly important way to treat a subset of the obese population. Treatment of the syndrome, however, is still in its infancy. One clinical trial has reported efficacy with the SSRI sertraline. Other treatments, such as the anticonvulsant topiramate, phototherapy and other SSRIs, may also offer future promise.