After the discovery of rapid eyeball movements and muscle tone changes during sleep, sleeping period was divided into several sleep states. Sleep states were staged by the patterns of EEG, EOG and EMG recordings during sleep. The terminology, techniques, and staging criteria of human sleep were suggested by Rechtschaffen and Kales in 1968. Several other physiological sleep parameters have been added to polygraphic sleep recording. In 1990, diagnostic criteria and polysomnographic findings of sleep disorders were described in the International Classification of Sleep Disorders (ICSD) by American Sleep Disorders Association(ASDA) in association with European Sleep Research Society, Japanese Society of Sleep Research, and Latin American Sleep Society. Recently, in 1999, International Federation of Clinical Neurophysiology (IFCN) published the second edition of IFCN Recommendations for the Practice of Clinical Neurophysiology for the purpose of standardization of routine clinical electrophysiological studies including polysomnography. The aim of his article is to introduce the principles and practical aspects of routine sleep recording procedures on the basis of three historical criteria and guidelines of routine sleep recording procedure called polysomnography.
