||We performed a retrospective chart review of 50 youths with Autism Spectrum Disorder (ASD), prescribed amitriptyline (AMI) for hyperactivity and impulsivity. Data was systematically extracted from 50 outpatient clinic charts, including AMI treatment duration, dose, trough levels and adverse events. Mean age was 9.4 years (4.6-17.9); 40 were males and 10 females. 30 % had failed atomoxetine and 40 % had failed ≥3 ADHD medications. Mean dose was 1.3 ± 0.6 mg/kg/day, mean trough level 114.1 ± 50.5 ng/ml, mean duration 3.4 years. Clinical Global Impressions Scale-Improvement (CGI-I) was ≤2 in 60 % of patients at the final visit, and in 82 % of patients for at least 50 % of follow-ups. Cautious use of low dose AMI shows promise for treatment-resistant youth with ASD accompanied by hyperactivity, impulsivity, aggression and self injury.