Objectives : We assessed the availability of Aberrant Behavior Checklist (ABC) for the evaluation of the pharmacological effect in autistic disorder. Methods : A retrospective review of the medical records of 27 children with autistic disorder, who visited the department of child and adolescent psychiatry of Kyungpook National University Hospital, from October 2011 to February 2013, was conducted. After treatment with risperidone, changes in the severity and improvement of symptoms were measured using ABC at the baseline, 2nd visit and 3rd visit, respectively. Results : The mean daily dose of risperidone increased from $0.66{pm}0.27mg$ (baseline, initial dose) to $1.02{pm}0.50mg$, 2nd visit, and $1.19{pm}0.50mg$, 3rd visit. According to ABC, irritability, lethargy, hyperactivity, and inappropriate speech subscale scores decreased significantly from the baseline to 2nd visit. Irritability and Hyperactivity subscale scores decreased significantly from the 2nd to 3rd visit. All subscales and total scores of ABC decreased significantly from the baseline to 3rd visit. Conclusion : The results of this study suggest that ABC can be used as an efficient tool to measure the symptoms of autistic disorder and to evaluate the medication effect on continuous treatment.