SUMMARY. Polysomnography is a medical diagnostic test which offers a large amount of information by recording the activity of various organ systems for a period of several hours with the aim of diagnosing pathological conditions associated with sleep. It is used for the diagnosis of apnoea-hypopnoea and upper airway resistance syndromes, and a variety of other sleep conditions related to daytime sleepiness that cannot be classified as breathing disorders, such as restless leg syndrome, disorders during REM sleep and other parasomnias. The first manual- report in Polysomnography published in 1968 by Rechtschaffen and Kales (R & K) contained scoring rules for the assessment of all parameters of sleep, and became a guide for thousands of polysomnographic tests. During the 40 years which have passed since the publication of the first manual, there has been vigorous development in the methodology of recording the parameters of polysomnography and the scoring rules. As a result of these developments, the American Academy of Sleep Medicine (AASM) published a new manual in 2007: The AASM Manual for the Scoring of Sleep and Associated Events – Rules, Terminology and Technical Specifications, which revises some of the rules and adds others concerning disorders and syndromes that have been described since the first edition of the manual. Πνεύμων 2008, 21(4):-.