OBJECTIVE To analyze the clinical manifestations,neuroimaging and pathological characteristics of primary central nervous system lymphoma (PCNSL)with a normal immunity,and to explore the methods of treatment and diagnosis.MKTHODS The clinical,laboratory,imaging data and pathological findings and therapeutic efficacy of 31 cases with pathologically proved PCNSL,during a period from July 1995 to June 2006,were analyzed retrospectively.The method of surgery,used in combination with chemotherapy and radiotherapy,was evaluated in 18 cases versus a simple surgical procedure used in 5.Among the total cases,a CHOP regimen was employed in 11 and Teniposide(VM26)plus Semustine (me-CCUN)was used in 7 cases.RESULTS PCNSL had a variety of clinical features,so that its misdiagnosis rate was high.The main clinical findings of PCNSL included intracranial hypertension and(focal)neurologic impairment.No positive result was found in the CSF cellular examination.All of the 31 cases were B-cell lymphoma.Twenty-four of the 31 cases were followed-up.with a follow-up period from 6 to 98 months.The median period of survival ofthegroup who underwent surqery in combination with chemotherapy and radiotherapy was 20 months,while the group with simple surgical therapy was 10 months.CONCLUSION Specific clinical manifestations were usually absent in the patients with PCNSL,giving an uncertain preoperative diagnosis and a poor prognosis.Pathological examination is the only reliable method for a final diagnosis of the disease.The main objective of surgical therapy is to relieve the intracranial hypertension caused by the tumor.Recurrence may occur in a short period following the simple operation.Therefore combined therapy,i.e.surgery plus additional radiotherapy and chemotherapy,should be adopted.This is the key point for extending survival time and improving the quality of life.