Primary central nervous system lymphoma constitutes only 1% of all intracranial tumors. Although survival time has increased by combined chemotherapy and radiotherapy, it still has a malign prognosis. A 62-year-old male patient presented with complaints of headache and forgetting. Cranial computerized tomography and magnetic resonance imaging demonstrated a mass in the left temporoparietal region extending to the posterior horn and trigone of the lateral ventricule. The case was diagnosed as lymphoma after stereotactic biopsy. There was a partial regression of symptoms after radiotherapy. The patient was lost due to local recurrence after 14 months.