The activation of oncogenes and the inactivation of tumor suppressor genes within neoplastic cells lead to transformation and loss of growth control. The key clinical feature that should arouse suspicion of a primary brain tumor and lead to a prompt evaluation is the progressive nature of the signs and symptoms, which include headaches, nausea and emesis, double vision, change in personality or cognition, speech difficulty, seizures and weakness. Neuroimaging with contrast-enhanced computed tomography or magnetic resonance imaging is the best method of confirming the presence of a primary brain tumor. Initial treatment in most patients is biopsy or surgical resection. For malignant and selected benign primary brain tumors, further treatment is necessary and may include radiation therapy, chemotherapy or experimental protocols.