**Abstract**

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia exclusively occurring during REM sleep. Viewing this disorder through a neurologic lens can provide longitudinal context for patients and their treating physicians, given the well-known association of RBD with a specific group of neurodegenerative disorders: the alpha synucleinopathies. It is important to have a high degree of clinical suspicion, the ability to make an accurate diagnosis, manage the symptoms, and more importantly monitor the patient for evolution of possible underlying neurological pathology. This chapter will discuss aspects of the clinical history, physical examination, ancillary testing, and diagnostic criteria.

**Keywords:** rapid eye movement (REM), REM sleep behavior disorder (RBD), Parkinson's disease (PD), alpha synucleinopathies, dementia with Lewy bodies (LBD)
