Objective: To provide an initial description of the effectiveness and pharmacokinetics (PK) of quetiapine in aggressive children with conduct disorder (CD). Method: This 8-week, open-label outpatient trial, enrolled patients ages 6 to 12 years with CD. Outcome measures included the Rating of Aggression Against People and/or Property Scale (RAAPPS), Nisonger Child Behavior Rating Form (NCBRF), and the Conners Parent Rating Scale (CPRS-48). Blood sampling for PK analyses occurred at the end of weeks 2 and 8. Results: Seventeen children (16 boys, mean age 8.9 years) were treated. The mean dose at week 8 was 4.4 mg/kg (SD = 1.1 mg/kg). Significant decreases in the baseline scores of the RAAPPS, and several subscales of the NCBRF and the CPRS were found by the end of the study (p less than 0.05). No patients discontinued because of an adverse event. No patients experienced extrapyramidal side effects. Quetiapine disposition was linear over the dose range studied. The elimination half-life of the drug averaged 3.9 and 2.9 hours and total body clearance averaged 3.5 and 3.0 L/hr/kg after study weeks 2 and 8, respectively. Conclusions: These preliminary data suggest that aggressive children with CD may benefit from quetiapine. The PK of quetiapine supports twice-daily dosing in children with CD. (Contains 2 figures and 3 tables.)