A fifteen-month-old child was admitted with a week history of isolated fever. On CSF (Cerebral Spinal Fluid) examination, hyperproteinorachy, hyperglycorachy and hypochlorurachy were found. The diagnosis of tuberculosis meningitis was suspected but usual tests were unable to find Mycobacterium tuberculosis in CSF, urine and sputum. Only the Polymerase Chain Reaction detected the Mycobacterium tuberculosis genome in the CSF. A specific treatment was started immediately. Apyrexia was obtained within 2 days; the outcome was favorable, without sequelae.