There is no single definition of pharmacoresistant (intractable, refractory) epilepsy. Prospective identification of pharmacoresistance is complicated by the variability of its appearance across different types of epilepsy and the variability of seizure control within a given patient over time. Failure of informative trials of two appropriate antiepileptic drugs has been recommended as a threshold that should trigger referral for evaluation at a comprehensive epilepsy center. Maximizing seizure control is imperative for reducing the risks and consequences of epilepsy, including the cognitive and psychiatric comorbidities and even sudden death.