The pharmacotherapy of epilepsy is a complex process guided by evidence-based research and clinical experience. Some patients achieve seizure freedom upon treatment with the first anti-seizure medication (ASM) prescribed, whereas others may be treated with two or three medications before one (or a combination) is found that reduces seizure frequency and/or severity with minimal side effects. Many patients demonstrate a partial response to treatment, leading to reduced seizure frequency and/or severity, but do not become completely seizure free. It is often stated that ~30% of epilepsy patients have seizures that cannot be controlled pharmacologically, and these patients are defined as having medication-resistant epilepsy (MRE). The International League Against Epilepsy (ILAE) published the following definition of MRE: ‘drug resistant epilepsy may be defined as failure of adequate trials of two tolerated and appropriately chosen and used ASM schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom’[1]. Treatment success or sustained seizure freedom is defined as one year without seizures or three times the inter-seizure interval (whichever is longer). The ILAE definition provides a useful standard from which to work, and MRE can be clinically identified in patients that fail to achieve seizure freedom after multiple ASM trials. However, the ILAE definition of successful treatment does not account for partial response to pharmacotherapy. Indeed, many partial responders have improved quality of life, even if they are not seizure-free for one year or more.