Ten female patients suffering from catamenial epilepsy were treated with a synthetic analogue of the gonadotrophin releasing hormone (GnRH) in addition to antiepileptic drugs. Three of the patients became seizure free, in four patients seizure frequency decreased and in one patient seizures were of shorter duration. In only two of the patients was there no therapeutic effect. Adverse effects, including hot flushes, headache and increase in weight, were noticed in eight patients. These results support the hypothesis that treatment with a synthetic GnRH analogue might be helpful in patients with intractable catamenial epilepsies.