Objective: Anticonvulsants are known to be effec-tive to manage affective instability and aggressive behavior by reducing neuronal excitability. This study examined the efficacy and safety of topiramate, a novel anticonvulsant, on disruptive behavioral problems in children and adolescents, with or without mental retar-dation (MR), and the differences of short-term efficacy and safety according to the IQ levels. Methods and Materials: Fifty-four children and adolescents with disruptive behavioral problems were enrolled in a 6-week, open-label study. All subjects were divided into 3 groups (subjects without MR, Non-MR; subjects with mild MR, Mild MR; and subjects with moderate to severe MR, Mod-Severe MR) based on their intellectu-al ability, and treated with topiramate. Outcome mea-sures included the Aberrant Behavior Checklist Hyperactivity (ABC-H) and Irritability (ABC-I) sub-scales and the Clinical Global Impression Severity (CGI-S) scale. Results: Significant reduction of CGI-S, ABC-H, and ABC-I scores were noted in all three groups in the following order: Non-MR, Mild MR, and Mod-Severe MR. Parethesia, anorexia, somnolence, nocturnal enuresis, and urinary frequency were rela-tively common adverse event. However, no serious adverse events were reported. Conclusions: Topiramate was effective and well tolerated for managing disrup-tive behavioral problems and emotional instability in children and adolescents.