To evaluate the incidence and the prevalence of drug-resistant epilepsies and risk factors in relation with this condition.The epidemiological approach of drug-resistant epilepsies come up against two major difficulties: the lack of a rigorous and consensus definition of this condition and its elusive evaluation which is indirectly appreciated with many studies concerning the remission of seizures in heterogeneous population of patients with or without treatment.The majority of papers on this topic report a hard core of 20 p. 100 of patients who continue to have seizures under treatment. This percentage has to be discussed because many factors can influence the exact number of patients with refractory epilepsy: the age of the first seizure, the seizure type, the cause of the seizures, the effective therapeutic interventions. This percentage did not seem to have been modified since the use of "new" anti-epileptic drugs and the development of epilepsy surgery. The main problem is to appreciate when refractoriness is really present and how long does it takes to declare that this condition has a self-perpetuating progression. Thank to the data from an abundant literature we can put forward that nearly 10 p. 100 of the incident cases could become refractory and that 1 to 2 /1 000 persons are drug resistant epilepsies, of which partial epilepsies represent 60 p. 100 of the cases. This rate allows to think that in France 5 000 to 12 000 patients may require a surgical evaluation and that annual need for surgery would be 500 patients per year.Data on drug-resistant epilepsies in France are lacking and it seems essential to put in place in our country a population-based incidence study including the risk factors of intractability in order to confirm these epidemiological data. The results of such a study would help to convince the political authorities to encourage the development of surgical structures.