Patients who are refractory to medical management can be candidates for surgical treatment such as anatomical or functional hemispherectomy. This chapter presents a case study of a 10-month-old male with left-sided hemiparesis. The patient subsequently developed seizures refractory to medical treatment and presented for a right functional hemispherectomy. Postoperatively, antithrombin III (ATIII) levels were checked twice daily and infusions of thrombate III were dosed accordingly. Early surgery for intractable epilepsy is recommended as it has been shown to improve functional outcomes. Anatomic hemispherectomy consists of the resection of the frontal, parietal and occipital cortices, complete temporal lobectomy and insular resection. Perioperative complications associated with this procedure include significant changes in systemic and pulmonary vascular resistance, arrhythmias, cardiac arrest, neurogenic pulmonary edema, seizures, cerebral edema, massive blood loss, and coagulopathy. Patients undergoing hemispherectomy are usually on chronic anticonvulsant therapy.