Cerebrospinal fluid (CSF) leakages either secondary (traumatic) or spontaneous (non-traumatic) are first considered in their frequency and origin. The exact topography of the various meningeal and cranial lesions involved are difficult to assess particularly in the most important groups of persistant traumatic CSF rhinorrhea and recurrent meningitis. Among the various diagnostic approaches, direct observation is always necessary, but of limited value. Standard X-rays must be followed by multidirectionnal tomography (Polytome) and, whenever available, computed tomodensitography of the base of the skull. Brain pneumography provides a thorough setting fourth of the congenital or acquired cerebral lesions as well as the new cranio-meningeal conditions. Difficulties encountered with the techniques of subdurography and Pantopaque injection are underlined. Three radioisotope techniques are considered. 1) The earlier technique of cotton-pledgets only shows the external orifice. 2) The recent proposal of nuclide cranial subdurography is criticized for ignoring the leptomeningeal bag. 3) Radioisotope cisternography (RIC) or gamma-cisternography is described more precisely. It remains the most complete and appropriate method for observing the natural behaviour of the leakage. RIC with fistulography is performed through suboccipital injection of 99mTc-DTPA. RIC provides essential clues on the relative importance of associated dynamic disturbances of the third circulation and morphological changes of its anatomical bed (stenoses and widenings of the ependymal and leptomeningeal spaces). If present, the leakage may be directly shown on the RIC pictures. If rhinorrhea is abundant, there is no difficulty in assessing side and site of the fistula. If rhinorrhea is occult, dubious or intermittent, diagnosis is often difficult. There are also indirect signs of rhinorrhea: leptomeningeal dilatation near a frontal or ethmoidal fracture, contamination of the rhinopharynx, examination of the handkerchieves for presence of radioactive material. Statistical results from the literature are summarized in a table.