Central disorders of hypersomnolence are characterized by daily periods of irrepressible need to sleep or daytime lapses into sleep, as defined in the current version of the International Criteria of Sleep Disorders. Thus, the unifying symptom is excessive daytime sleepiness which is not caused by any other sleep-wake disorder. Relevant disorders including narcolepsy type 1 and 2, idiopathic hypersomnia, Kleine-Levin syndrome, and insufficient sleep syndrome will be discussed. Other central disorders of hypersomnolence include hypersomnias due to medical or psychiatric disorders or because of medication or substance use.In sleep-related movement disorders, the cardinal symptom consists of simple, often stereotyped movements occurring during sleep. The most frequent disorder in this category of sleep-wake disorders is restless legs syndrome, which is often associated with period limb movements during sleep.