The spinal fluid examination was performed in 180 cases of histologically verified intracranial tumors. Cisternal puncture was done in all cases. The authors conclude: 1) Hypertension, increased cell count and increased protein value are found with more frequency and intensity in intracranial lesions of rapid growth; 2) Hypotension is frequent in cases of subdural hematomas; 3) Spinal fluid hypertension corresponds to the clinical symptoms of intracranial hypertension, although this is not always the case; 4) High protein value is commonly found in cases of acoustic neurinoma; 5) The presence of eosinophils above 2 per cent has diagnostic value in cases of cerebral cysticercosis, being a more constant element than complement fixation test; 6) The absence of spinal fluid during the cisternal tap was considered as suggestive of posterior fossa tumor.