Cyclic vomiting syndrome (CVS) is manifested by episodic occurrence of emesis that may be precipitated by stress and fatigue. The attacks begin in childhood and often taper in frequency into young and middle adult life. They frequently occur in clusters with intervening normal periods of days, weeks, months, or years. In these regards, CVS shares similarities with many other episodic disorders of brain, heart, and skeletal muscle. These disorders include the periodic paralyses, episodic movement disorders, cardiac dysrhythmia syndromes, epilepsy, and migraine headache. Because of some of the similarities among these disorders, it has been hypothesized that common pathophysiologic mechanisms may underlie some of these disorders. CVS may also share a similar pathophysiologic basis, and this idea may lead to novel approaches to investigation of this fascinating and difficult disorder.