Sleep disorders and neurodegenerative diseases are commonly encountered in primary care. A common, but underdiagnosed sleep disorder, rapid eye movement sleep behavior disorder (RBD), is highly associated with Parkinson disease and related disorders. Rapid eye movement sleep behavior disorder is common. It is estimated to affect 0.5% of the general population and more than 7% of individuals older than 60 years; however, most cases go unrecognized. Rapid eye movement sleep behavior disorder presents as dream enactment, often with patients thrashing, punching, and kicking while they are sleeping. Physicians can quickly assess for the presence of RBD with high sensitivity and specificity by asking patients the question "Have you ever been told that you act out your dreams, for example by punching or flailing your arms in the air or screaming and shouting in your sleep?" Patients with RBD exhibit subtle signs of neurodegenerative disease, such as mild motor slowing, constipation, or changes in sense of smell. These signs and symptoms may predict development of a neurodegenerative disease within 3 years. Ultimately, most patients with RBD develop a neurodegenerative disease, highlighting the importance of serial neurological examinations to assess for the presence of parkinsonism and/or cognitive impairment and prognostic counseling for these patients. Rapid eye movement sleep behavior disorder is treatable with melatonin (3-6 mg before bed) or clonazepam (0.5-1 mg before bed) and may be the most common, reversible cause of sleep-related injury. Thus, it is important to identify patients at risk of RBD in a primary care setting so that bedroom safety can be addressed and treatment may be initiated.