Continuous spikes and waves during slow sleep (CSWS) is a syndrome with a serious prognosis due to the frequent association with neuropsychological dysfunction. It is mandatory to consider this syndrome if an epileptic child suffers from behavioral changes, dysarthria or learning difficulties. We report on two patients with CSWS syndrome with focal abnormalities on the nondominant hemisphere and a proportion of generalized spike-waves discharges in more than 85% of their NREM sleep on the EEG. Both had a good response to the treatment with sodium valproate and ethosuximide at high doses. Both suffered a relapse of their clinical and EEG semiology after withdrawal of their treatment. After restarting treatment they became clinically normal with a normal sleep EEG recording. We propose the association of sodium valproate and ethosuximide for CSWS; this treatment should be maintained until adolescence.