This paper emphasizes our approach to control increased ventricular fluid volume and pressure; it utilizes an improved device based upon hydrostatic pressure principles. Intracranial pressure may be maintained at any preselected value, usually 25 cm H2O. Pressure increases beyond this value will result in a venting of fluid into a calibrated reservoir. The hydrostatic column will act to cushion the surrounding ventricular mass, helping to prevent ventricular collapse. The method overcomes the hazards of techniques, using intermittent withdrawal of fluid which requires human judgment. Ventricular pressure response curves performed on a number of patients showed a marked stability with a response less than 2 mm Hg/ml. This indicates a favorable influence on the intracranial compliance. The system is completely closed and its use in 52 neurosurgical patients in over 400 patient days has not been associated with any infection problem.