: Disorders of gut-brain interaction (DGBI), characterized by chronic abdominal pain and significant disability, affect 15-20% of children and adults and continue into adulthood in ~60% of cases. Costs for adults reach USD 30 billion per year, yet effective management strategies are elusive. Studies support using cognitive behavioral therapy (CBT), but abdominal pain only improves in ~40% of patients. Dietary management (low FODMAP diet; LFD) has also shown promise but it is effective in only a similar percentage of patients. Studies suggest that biologic factors (biomarkers) contribute to CBT response. Similarly, gut microbiome composition appears to influence abdominal pain response to the LFD. However, no previous CBT trials in children or adults have measured these biomarkers, and it is unclear which patients respond best to CBT vs. LFD. : Children aged 7-12 years with DGBIs ( = 200) will be categorized as having/not having Autonomic Nervous System imbalance and/or abnormalities in gut physiology. We will randomize these children to either CBT or a LFD to compare the effectiveness of these treatments in those with/without abnormal physiologic biomarkers. We hypothesize that CBT will be more effective in those without abnormal physiology and LFD will be more effective in children with abnormal physiology. Primary outcome measures include the following: (1) Symptom improvement (abdominal pain frequency/severity) and (2) improvement in health-related quality of life. : This innovative multidisciplinary study is the first to identify physiological characteristics that may moderate the response to two different management strategies. Identification of these characteristics may reduce the burden of these disorders through timely application of the intervention most likely to benefit an individual patient.