An assessment model for evaluating sedation in pediatric dental patients has been described. The model in whole or in part can be a valuable asset in drug trials and clinical evaluations. The unique characteristics of this model include: assessments are easily and quickly carried out without interruption of normal patient care; the criteria for sedation behavior can be standardized and are clinically relevant; a determination of the level of consciousness using an airway obstruction maneuver permits an assessment of safety; and the reliability of the observer ratings is extremely high, thereby avoiding the necessity of specially trained personnel. Using the assessment procedure, a placebo-controlled, double-blind clinical trial of various doses of chloral hydrate with and without N2O was performed. The results indicate that: children receiving the placebo treatment behaved favorably for at least 46% of the ratings; the 20 mg/kg and 40 mg/kg chloral hydrate groups showed little or no improvement when compared with the placebo group; the group receiving 60 mg/kg chloral hydrate had as much as a 33% improvement in behavior as compared with placebo; and with the addition of 40% N2O/60% O2 to 60 mg/kg chloral hydrate premedication, four of 15 children (27%) were unable to maintain a patent airway when intentionally obstructed.