Abstract: Recurrent abdominal pain (RAP) is the cause of disruption of daily activities/missed school days, overutilization of healthcare, unnecessary surgeries, and anxiety in 10 to 15% of children. Its etiology is not clearly understood, however, the success of several clinical protocols suggests that autonomic dysregulation is a factor. This study compared autonomic activity, including heart rate variability (HRV), in 30 children between the ages of five and 17 years old with and without RAP. Demographic information was obtained from both groups. Physiological measures given to both groups included cardiac time and frequency domain measures and respiratory measures obtained during ambulatory monitoring. Physiological data as well as pain severity and frequency information was also collected from the RAP group during HRV biofeedback treatment sessions to determine if autonomic balance could be improved along with RAP symptom reduction. Results revealed that children with RAP have significantly different autonomic functioning than children without RAP at time one (baseline), and the RAP group was able to significantly reduce their symptoms which was correlated with their ability to significantly increase their autonomic balance after completing HRV biofeedback. Pending verification from future studies, the results are very promising. While it remains unknown whether or not the present intervention is more effective than other interventions, such as hypnosis or cognitive-behavioral therapy, the present study has found that both patients and parents readily accepted HRV biofeedback treatment. It also fits easily in a pediatric medical setting in that it is relatively inexpensive to conduct sessions, the equipment is portable, and sessions can be conducted in a small work space. The present study also sheds light on potential criteria for positive diagnostic purposes for patients with RAP. Having positive indicators of RAP would be instrumental in eliminating the many invasive procedures, which must now be used in order to rule out other diagnoses. Determining the common factors in all RAP cases is greatly needed to expand the understanding of RAP and to assist in better treating those afflicted with this disorder.