Brain metastasis is a sign of advanced malignant disease. The grave clinical symptoms demand an immediate and accurate diagnosis and effective palliation. Computer-assisted tomography with contrast enhancement is the most established diagnostic procedure, and the number and size of the metastases can be determined, as well as indirect signs of increased intracranial pressure. The treatment of choice for multiple brain metastases is whole-brain irradiation. The symptomatic responses range between 60% and 80%, with a median survival of about 5 months. Survival in individual cases however, is mainly influenced by the histology of the primary tumor, as well as the general condition of the patient and the progression of the extracerebral disease. Prophylactic brain irradiation in patients with small-cell lung cancer and a good response to chemotherapy significantly decreases the incidence of symptomatic metastases in patients and yields longer survival times. Larger treatment doses per fraction and simultaneous application of chemotherapy may enhance the risk of late neurological sequelae.