SummaryThe authors had the opportunity to apply different techniques of encephalography in the investigation of cerebral arachnoïditis, supra- and infratentorial tumour cases.They illustrate de value of fractionated encephalography by the report of some observations. These concern unspecific optochiasmatic and cerebello-pon-tine arachnoïditis, adhesive tuberculous meningitis cases and also cerebellar haemangioblastoma, pontine astrocytoma and acoustic neurinoma cases.