Over the past decade, studies have shown improved survival in patients with locally advanced non-small-cell lung cancer. This can be attributed to better systemic therapy, growing experience with combined-modality therapy, technologic advances allowing for increased radiation doses, better supportive care, and better patient selection. With longer survival, we are seeing an increase in the incidence of central nervous system (CNS) metastases. Prophylactic cranial irradiation (PCI) decreases the incidence of CNS metastases in these patients and may have a favorable impact on quality of life and overall survival. This paper reviews the incidence of CNS metastases in non-small-cell lung cancer patients, past experience with PCI, and a current study evaluating the impact of PCI on survival, neuropsychological function, and quality of life.