Aims  and objective: To Study correlation of CSF–ADA level in TBM. Study design: A prospective study was conducted civil hospital, BJMC Ahmedabad, Department of pediatrics  Results: In this study among  50 cases of meningitis, 34(68%) patients were of TBM. Most common presenting symptom in  TBM patients was fever(94%). Among all TBM 19(55.88%) patients had CSF protein value between 100–200mg. 02(05.88%) patients with value >200 mg% had adverse prognosis. Maximum patients 25(73.53%)  had CSF cell count <100 cells/ cu.mm with mononuclear cell predominance. Most common changes on imaging was hydrocephalus (9/20 on CT and 6/14 on MRI). CSF ADA was positive in 21(61.77%) patients. Out of  16 nonTB patients,3 had positive CSF ADA value.CSF ADA has 61.77% sensitivity and 81.25% specificity with positive and negative predictive value of 87.5% and 50%, we thus conclude that CSF ADA is an important investigation in early diagnosis of TBM.