Context. Gabapentin is reported to have an analgesic effect of reducing phantom-limb pain (PLP) in adult patients. There is no study on preoperative use of gabapentin in pediatric population in terms of PLP prevention. Objective. To determine whether gabapentin could be used as an adjuvant agent of opioid-based pain control to lower the rate of PLP in pediatric patients undergoing amputation for malignant bone tumors in observation period of 60 days postoperatively. Methods. Pediatric patients who were diagnosed with osteosarcoma or Ewing's sarcoma around the knee and underwent amputation from May 2013 to March 2016 were registered to this prospective double-blind randomized controlled trial. Four days before amputation, the patients were randomized to a study group receiving oral gabapentin, and a control group receiving oral placebo, both for 30 days. Pain intensity was recorded using the visual analog scale at different time points in all patients. PLP was assessed daily during their postoperative hospital stay and at the last follow-up visit 60 days after operation. Results. Of the 45 patients included in our study, 23 patients were randomized to gabapentin group and 22 to placebo group. There was no significant difference in preoperative baseline pain intensity between the two groups (P = 0.12). The overall postoperative pain intensity in gabapentin group was significantly lower than that in placebo group (P < 0.05). The rate of PLP in gabapentin group was significantly lower than that in placebo group (43.48% vs. 77.27%, P = 0.033) at the last follow-up visit. Conclusions. In pediatric patients, gabapentin shows the effect of preventing PLP and reducing postoperative pain intensity in acute period after amputation. Initiation of gabapentin therapy as an adjuvant to opioids before amputation is beneficial with no severe adverse effect. (C) 2017 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.