Cyclic vomiting syndrome (CVS) is a paroxysmal, recurrent vomiting disorder of unknown pathophysiology and target organ. It has been hypothesized that CVS shares the same mechanism as migraine. We describe here a 5-year-old boy with CVS characterized by episodic vomiting attacks. These recurrent vomiting episodes began at 3 years of age, occurred every month and lasted for 5 days at a time. At the time of admission, no abnormal physical or neurological findings were observed and laboratory findings, including brain MRI and endoscopic examination, revealed nothing specific. The vomiting episodes were self-limited but recurrent and severely interrupted his daily life. When this patient was treated with topiramate, he showed a marked increase of symptom-free periods.