Various estimation of the proportion of difficult-to-treat epileptic patients is given in the literature. It varies from 5 percent to 25 percent, because of imprecise meaning of pharmacoresistancy and similar terms. There is no such thing as a unique pharmacoresistant epilepsy. Persisting seizures despite antiepileptic drug prescription does not necessarily mean refractory seizures. Seizures may be drug-resistant for a limited period only, or be intermittent, or be a long-lasting condition. Seizure frequency may remain unchanged, or decrease, more or less. Toxicity of AEDs must be considered. Unbearable side effects are a limiting factor for maintaining some active drugs. In practice, the term pharmacoresistancy may be used when seizures occur in spite of a convenient therapy, whatever their frequency, and whatever the resulting handicap. Predictive factors for intractibility may be considered under four headings, i.e. seizure types, patient, epileptic syndrome, and antiepileptic drugs. Most of the elements of the first three groups are available immediately after the first seizure and response to treatment may be estimated one or two years later. Outcome of an epilepsy may be evaluated, or guessed, rather early. This is crucial for management of epileptic patients.