In treatment of epilepsy with anti-epileptic drug (AED), it is important to long-term commitment and compliance from the patient. Many factors such as seizure types, metabolism, drug interactions, comorbidities, and side effect were considered when selecting AEDs. Long-term retention rate can give much information about a certain drug to clinicians and increase compliance and anti-seizure effect Topiramate (TPM) is new generation AED and has several pharmacological properties that account for the broad-spectrum profiles. TPM approved in Korea in 1998 and used popular for monotherapy and adjunctive therapy in epileptic patients. The 1 year retention rate in TPM was 40-60% and 3 year rate were 30-40%. The reasons for TPM discontinuation was ineffectiveness in early phase and side effects in later phase. The frequent side effects to discontinue TPM were cognitive change such as mental slow. The similar rate between 1-year and 3-year suggest that side effect of TPM appear early period.