In briefSleep disturbances at high altitude may be caused by simple physical discomforts but may also be a symptom of acute mountain sickness (AMS). Nevertheless, restful sleep is necessary to perform work optimally the next day. Acclimatization is the best way to prevent AMS, but if drugs are used to promote sleep, acetazolamide is the drug of choice. During tests on Mt. Logan, all subjects said they slept better and had less morning headache after using acetazolamide. The amount of Cheyne-Stokes breathing was reduced, arterial oxygen saturation was improved, and there was no profound hypoxemia. Traditional sedatives are often used but should be used with caution because they can worsen sleep hypoxia, impair judgment and coordination the next day, and turn a climb into a life-threatening situation.