Cyclic vomiting syndrome is an idiopathic disorder characterized by attacks of severe vomiting, interspersed with normal periods, and found in patients with a family history of migraine headaches. In this report, we investigated the characterization of the autonomic abnormalities in cyclic vomiting syndrome, contrasting them with values in pediatric population, as well as adults with migraine headache. We studied five groups: 41 normal pediatric controls (NPC), 12 patients with pediatric chronic vomiting (PCV), 15 patients with cyclic vomiting syndrome (CVS), 21 adults patients with migraine headaches (MHA), and 40 normal adult controls (NAC). We studied the sympathetic and cholinergic functions: two measures of sympathetic adrenergic function-vasoconstriction to cold and postural adjustment ratio; two measures of vagal cholinergic function--Valsalva ratio and ECG R-R interval; and one measure of total autonomic score. Comparisons were performed between and within groups by t tests and reported as mean +/- SEM. Although cholinergic function measures were lower in cyclic vomiting and migraine groups, the most distinct abnormality was low postural adjustment ratio in both cyclic vomiting and migraine groups vs normal pediatric and pediatric chronic vomiting groups. There was also a significant difference between cyclic vomiting and pediatric chronic vomiting groups (P < 0.05 in three other parameters). Cyclic vomiting syndrome is associated with distinctive adrenergic autonomic abnormalities similar to those in patients with migraine headaches and is usually characterized by a low postural adjustment ratio. These findings may have implications for both confirmation and diagnosis of cyclic vomiting syndrome.