During polysomnography brief arousals are clinically important and increasingly scored. However, the frequency of arousals during routine polysomnography in the normal population is unknown. We performed overnight polysomnography in the 55 control subjects from a general private practice list who were approached and agreed to undergo polysomnography. Awakenings were scored according to the criteria of the American Sleep Disorders Association (ASDA). There was a mean of 4 (95% confidence interval (CI)), awakenings per hour, whereas the ASDA definition gave 21 per hour slept. In our subjects,arousal frequencies increased significantly (p < 0.001) with age, who ranged from the late teens to early 70s. The high upper limit of the frequency of brief arousals was not altered by exclusion of patients who snored or had witnessed apneas or daytime sleepiness. It is important that those scoring arousals on routine polysomnography recognize that high arousal frequencies occur in the normal population on night polysomnography.