BACKGROUND & AIMS: There are no prospective, multicenter, double-blind, placebo-controlled, randomized pharmacologic trials for the treatment of pain-predominant functional gastrointestinal disorders in children. The aim of this study was to evaluate the efficacy of amitriptyline in children with pain-predominant functional gastrointestinal disorders. METHODS: In this multicenter placebo-controlled trial, children with irritable bowel syndrome, functional abdominal pain, or functional dyspepsia were randomized to 4 weeks of placebo or amitriptyline (10 mg/d, weight <35 kg; 20 mg/d, weight >35 kg). Assessment of gastrointestinal symptoms, psychological traits, and daily activities occurred before and after intervention. Pain was assessed daily with self-report diaries. The primary outcome was overall response to treatment (child's assessment of pain relief and sense of improvement). Secondary outcomes were effect on psychosocial traits and daily functioning. RESULTS: Ninety children were enrolled, and 83 completed the study (placebo, 40 children [30 girls]; drug, 43 children [35 girls]). A total of 63% of patients reported feeling better and 5% feeling worse in the amitriptyline arm compared with 57.5% feeling better and 2.5% feeling worse in the placebo arm (P = .63). Pain relief was excellent in 7% and good in 38% of children receiving placebo compared with excellent in 15% and good in 35% of children treated with amitriptyline (P = .85). Logistic regression analysis of those reporting excellent or good response versus fair, poor, or failed response showed no difference between amitriptyline and placebo (P = .83). Children who had more severe pain at baseline in both groups (P = .0065) had worse outcome. Amitriptyline reduced anxiety scores (P < .0001). CONCLUSIONS: Both amitriptyline and placebo were associated with excellent therapeutic response. There was no significant difference between amitriptyline and placebo after 4 weeks of treatment. Patients with mild to moderate intensity of pain responded better to treatment.