We report the case of a patient who was admitted to the hospital because of language and mental confusion. His initial lumbar puncture revealed 193 leukocytes per mm3 mostly lymphocytes (95%), no red blood cells, high protein content (1.20 g/L) and normal glucose level. The antibiotic therapy by amoxicilline and aciclovir during 6 days led to complete clinical recovery in a week. A CT scan of the cerebrum showed no abnormalities, nor did chest radiography. Twelve days after discharge, the patient was rehospitalized because of a meningitis syndrome. On lumbar puncture, the CSF analysis revealed 280 leukocytes/mm3, 56% lymphocytes, 10% monocytes and 34% polymorphonuclear cells. CSF chemistry showed a protein level of 3.54 g/L, and a glucose level depressed at 0.9 mmol/L. Because of the clinical symptoms and CSF abnormalities, the patient received aciclovir, amoxicilline vancomycine, isoniazide, rifampicine, pyrazinamide and ethambutol. Screening for infections gave negative results until the 37th day, when the diagnosis of tuberculous meningitis was confirmed by the isolation of Mycobacterium tuberculosis in the repetitive CSF. Antituberculous therapy was expanded. According the Reiber diagrams, intrathecal IgG synthesis was negative at day 25, day 37, month 4, month 9, month 17. Intrathecal IgM synthesis was elevated at day 12 and day 25 and intrathecal IgA synthesis at day 25. Improvement of the patient's conditions by tuberculosis treatment was obtained in 17 months. Cerebrospinal fluid analysis has been the basis for the diagnosis and follow-up of tuberculous meningitidis.