Clinical polysomnography has evolved considerably since Rechtschaffen and Kales1 produced the first manual of techniques and a scoring system for sleep stages of human subjects in 1968. A number of technical innovations have been introduced for the acquisition and recording of physiologic signals during sleep. Many of these innovations are intended to improve detection of sleep-related breathing disorders, the most common conditions for which polysomnography is performed. In addition, the development of continuous positive airway pressure and related therapies has added an important disease management dimension to sleep recording. Within the realm of neurology, several conditions are now defined primarily on the basis of polysomnographic criteria, including periodic limb movement disorder, rapid eye movement (REM) sleep behavior disorder, overlap sleep disorder, idiopathic hypersomnia, and narcolepsy without cataplexy. And with the emergence and refinement of digital electrographic recording during the past 3 decades, the field has been transformed by a proliferation of proprietary digital systems for the use of sleep recording. All of this progress has culminated in a critical need for comprehensive new standards for the acquisition and interpretation of sleep records. The American Academy of Sleep Medicine (AASM) took the lead to address this situation by organizing a task force composed of experts in the field who undertook a thorough review of the relevant literature and produced the first standard manual of digital polysomnographic technique and scoring in 2007. This landmark effort has significantly modified sleep recording and stage scoring, and has also standardized techniques and criteria for recording and recognizing a variety of sleep-related events, including obstructive and central apneas, hypopneas, periodic limb movements, electroencephalographic (EEG) arousals, and abnormal motor activity in REM sleep.