Twenty patients of tuberculous meningitis (TBM) in age group of 6 months to 10 years included in the study were divided into two groups of 10 patients each. Rifampicin was administered in dosage of 10 mg and 7.5 mg/kg bw to each patient of groups I and II respectively. Drug concentrations in serum and CSF of these patients were measured by a microbiological tube dilution method using a strain of Sarcina lutea. In group I mean serum and CSF concentration was 3.84 micrograms/ml and 0.178 microgram/ml respectively, while in group II it was 2.16 micrograms/ml and 0.206 microgram/ml respectively. These concentrations were many times higher than the MIC against Mycobacterium tuberculosis. Mean percentage penetration of rifampicin in CSF was 5 and 10% in group I and II respectively. We recommend similar studies in large number of children before advocating the therapy with low dose of rifampicin in TBM.