This trial sought to evaluate our experience using the antimigraine prophylactic drug, use of valproate for the prophylactic management of cyclic vomiting syndrome (CVS) in children. Thirteen children diagnosed with severe CVS were enrolled. Prophylactic therapy consisted of valproate administered at a dose of 10-40 mg/kg/day. Upon enrollment in the study, all patients underwent diagnostic tests to rule out organic causes of their symptoms. Vomiting was severe enough in all patients to cause dehydration requiring hospitalization for intravenous rehydration. Nine of 13 patients did not respond to numerous previous medical therapies like propranolol, amitriptyline, cyproheptadine, phenobarbital, phenytoin, and carbamazepine. Three of 13 patients required combination therapy with valproate and phenobarbital. Of the 13 patients, two showed complete resolution of their symptoms, nine had marked improvement in their symptoms, as evidenced by infrequent attacks of reduced severity, and two failed to respond to valproate therapy. Four patients experienced relapse with a decreased dosage of valproate. Side effects associated with long-term valproate administration were not observed. Valproate appears to be effective for the prophylactic management of severe CVS, with 85% of all patients achieving at least a reduction in the frequency of attacks.