Clobazam is a benzodiazepine with special molecular structure (its nitrogen radicals are in positions 1 and 5, rather than 1 and 4 as in all other antiepileptic benzodiazepines), and it is rapidly effective--in a matter of hours or within a few days--against all varieties of epileptic seizures in 52% of subjects treated with it. Its effects are relatively mild. Unfortunately, its outstanding antiepileptic properties are exhausted after only a few weeks in one-third of all cases. The authors discuss the potential significance of this phenomenon, and stress the urgent need for intensive study of the basic mechanism governing exhaustion of the antiepileptic properties of the benzodiazepines in general and clobazam in particular.