原發性中樞神經系統淋巴瘤約佔節外非何杰金氏淋巴瘤之1-2% ；近年來報告病例有增加趨勢。中樞神經系統淋巴瘤通常以B細胞淋巴瘤多，CT或MR的表現特徵在大腦半球腦室旁成單一或多發性腫塊。其治療以methotraxate為基礎之組合式化學治療併全腦40 Gy - 50 Gy放射線治療或加上腫瘤部分1400 cGy - 1440 cGy加強，結果可獲得較長生存期。但晚期神經毒性症狀亦相對增加。本文提供三例原發性中樞神經系統淋巴瘤之診斷及治療，兩位女性，一位男性愛滋病併發中樞神經系統淋巴瘤，診斷及治療時年齡皆低於50歲，兩位預後較佳者分別存活8 年及6年，愛滋病患則預後不佳，只生存8個多月。

Primary central nervous system lymphoma (PCNSL) comprised 2% of extranodal non-Hodgkin's lymphoma and 1-2% of primary intracranial tumor. The main pathohistologic type was high grade B-cell origin. PCNSL presented multifocal parenchymal lesions or leptomeningeal infiltration in the brain. The incidence increased in the patients associated with immunocompromised condition. We presented 3 cases with pathologically-proved PCNSL, one of whom is a young man with AIDS and the others are female, age below 50. They received chemotherapy and brain irradiation of 5000 - 5440 cGy. The methotrexate-based regimen was the effective chemotherapy. The patient with AIDS died at 8 months after completion of radiotherapyand another 2 were alive for 8 and 6 years respectively until last follow-up.