The long-term outcome of 75 children who underwent methyl methacrylate cranioplasty over a 15-year period is presented. Forty-two patients underwent cranioplasty for posttraumatic skull defects and 33 for nontraumatic causes. Within 8 years following initial cranioplasty procedure, a total of 17 (23%) complications occurred. Several factors correlated with the development of complications, including postoperative radiotherapy, the size of the defect, involvement of the frontal sinus, and the presence of prior infection. The authors currently recommend avoiding methyl methacrylate cranioplasty in selected patients who have received postoperative radiation therapy, in patients with large cranial defects, involvement of the frontal sinus, or any history of prior infection.