• Of 88 patients with intractable epilepsy, 60 have been treated with clonazepam for up to three years and 60 have been treated with sodium valproate for up to 18 months. Each agent was used sequentially in an overlapping group of 32 patients. Both agents have proven effective in the control of petit mal absences and myoclonic jerks, although some patients responded to one and not to the other. Clonazepam has given better results than valproate in temporal lobe and other partial (focal) epilepsies, while valproate has given better results in grand mal seizures and atonic attacks. Both preparations were more effective in patients with spike and wave paroxysms in their EEG recordings, the correlation being more conspicuous with valproate. Both medications appear to be safe and useful additions to anticonvulsant therapy.