Whole brain radiotherapy (WBRT) is the treatment of choice for the majority of patients with brain metastases. WBRT yields high radiologic response rate (27~56%) and is effective in rapid palliation of neurologic symptoms as well as prolongs time to neurocognitive function decline caused by intracranial lesions. By using conventional fractionation, 33% of patients developed late neurocognitive toxicity while memory impairment was the most common symptom. The incidence is even higher when a formal and sensitive neurocognitive assessment was prospectively evaluated. With more long-term survivors nowadays, it has become increasingly important to minimize neurocognitive function decline and maintain quality of life in patients with brain metastasis.