Thanks to the recent advance and development in science and technology extremely small quantities of substances of the cerebrospinal fluid (CSF) can now be measured. However, the measurement of these substances can not be done routinely. While, the classical CSF tests such as CSF pressure, cells, total protein and glucose are still usefull for the daily clinical diagnosis of neurological diseases. Here I report the ordinary CSF findings in acute viral meningitis and encephalitis, though the exceptions are not rare. In Creutzfeldt-Jakob disease the lately reported discovery of the 14-3-3 brain protein in the CSF will make a great impact on the diagnosis and clarification of pathogenesis of the disease.