Sleep and sleep deprivation have become major health issues in our modern society. Impaired sleep can negatively affect physical and psychological well-being, and conversely, certain common conditions can impair sleep. Furthermore, insufficient or disrupted sleep can contribute to functional impairments. As health care professionals, physical therapists are singularly concerned with function and well-being. To understand the role of sleep and sleep deprivation on health, this article describes sleep, our contemporary culture of sleeplessness, insomnia, sleep needs, the physical cost of inadequate sleep, the psychological cost of sleep deprivation, and the effects of sleep debt on safety. How to assess an individual's sleep debt is then described, and a sleep inventory questionnaire and scoring scale are presented. Evidence-based recommendations for optimizing sleep are outlined, and these can be readily implemented by the busy clinician. The sleep inventory questionnaire can be used to evaluate the outcome of these recommendations or other interventions as well as serve as an assessment tool. Based on the literature, the assessment and evaluation of sleep and basic sleep recommendations need to be considered as fundamental clinical competencies in contemporary physical therapy care.