The objectives of this study were to determine if the presence of ethanol (ETOH) in patients 10 to 20 years of age is associated with injury and if the patient's mental status reliably predicts their blood ethanol concentration. The study was designed as a retrospective, case-controlled report from a children's hospital emergency department. The data are from 45 patients 10 to 20 years old in whom ETOH was detected on toxic screen and 37 patients (N-ETOH) 10 to 20 years old in whom a toxic screen did not reveal ETOH. Injury occurred in 51% of the ETOH group and 8% (P = 0.0001) of the N-ETOH group. A correlation between blood ETOH level and mental status was found only at the extremes of blood ETOH levels. We conclude that the presence of ETOH may predispose adolescents to injury, requiring treatment in an emergency department. Except at the extremes of ETOH levels, mental status does not predict blood levels. A prospective assessment of mental status and blood ETOH levels in adolescents is needed before mental status assessment can replace the determination of blood ETOH concentrations.