Abstract Purpose of Review We describe the evolution and limitations of current diagnostic criteria and classification systems of CNS hypersomnolence disorders and propose some changes. Recent Findings An unsupervised cluster analysis of 1100 Europeans with hypersomnolence identified the narcolepsy type 1 phenotype but not other categories listed in ICSD-3. Summary There are long-standing unsolved issues regarding the diagnosis and classification of central disorders of hypersomnolence. These include delineating and identifying phenotypes and unique conditions (“sui generis”), sleep deprivation’s impact on phenotypes and how to separate sleep deprivation as a trigger from other causes, as well as the association of excessive sleepiness with other disorders. We discuss these issues and present a novel, straightforward classification system with consistent terminology to get out of the impasse and do justice to people with hypersomnolence.