Cyclic vomiting syndrome(CVS) is a disorder of unknown etiology that is characterized by its clinical pattern of intermittent episodes of severe vomiting, similar in time of onset and duration, with no symptoms during the intervening period. By definition, CVS is an idiopathic disorder that requires exclusionary laboratory testing. Not only can it be mimicked by many specific disorders, eg, surgical, neurologic, endocrine, metabolic, renal, but within idiopathic CVS there may be specific subgroups that have different mechanisms. It has been reported that CVS usually begins in toddlers and resolves during adolescence. Migraine is also self-limiting episodic condition of children and the clinical features of migraine and CVS show considerable similarity. It is proposed that CVS is a condition related to migraine. This paper reports clinical courses of long term follow-up and reversible EEG changes in three patients whose history included CVS. Clinical situations of attack interval, duration and associated symptoms had changed variablely in each patients through long term follow-up period. Cyclic vomiting subsided in two cases. Abnormal delta activity was seen during episodes and resolved at follow-up, when the patient asymptomatic. The brain wave changes support the interpretation of CVS as a migraine variant.