1. Introduction -- 2. History of CSF -- 3. Anatomy of CSF-related spaces -- 4. Physiology of CSF -- 4.1. CSF production -- 4.2. CSR resorption -- 4.3. Biological function of CSF -- 5. CSF collection -- 5.1. Techniques -- 5.2. Counter-indications and complications -- 5.3. Preanalytical aspects -- 6. Methods -- 6.1. Cell counts and cell staining -- 6.2. Glucose and Lactate -- 6.3. Proteins -- 6.4. Albumin -- 6.5. Immunoglobulins -- 6.6. Detection of infectious agents -- 6.7. Immunohistochemistry -- 6.8. Others (biomarkers) -- 7. CSF in clinical syndromes -- 7.1. Inflammatory disease of the CNS -- 7.1.1. Acute (bacterial, viral meningitis) -- 7.1.2. Chronic (MS) -- 7.2. Inflammatory diseases of the PNS -- 7.2.1. Acute (GBS, Neuroborreliosis) -- 7.2.2 Chronic (CIDP) -- 7.3. Neoplastic and paraneoplastic neurological disorders -- 7.4. Dementias and degenerative disorders -- 7.5. Cerebral bleedings -- 7.6. CSF rhinorrhoea and otorrhoea. 8. Guidelines.