Healthy or diseased, slim or obese, male or female, sedation cancause upper airway obstruction, which should be clearly differentiated fromhypoventilation. Upper airway obstruction is far more common & moredangerous. It is reassuring that significant unpleasant events can beprevented by careful preoperative assessment, along with attentiveintraoperative monitoring and postoperative care. Nevertheless, we must beprepared to manage unpleasant events should they arise. The aim of thisreview is to focus on upper airway collapse during sedation in relation todifferent drugs used in sedation in different clinical & experimentalconditions with a close reference to patient related factors augmenting theproblem, preoperative detection of susceptible patients, and intraoperativemanagement of such a problem.