SummarySix rabbits were subjected to a severe diffuse brain injury by injection of a small amount of olive oil into one internal carotid artery, and the blood pressure, ventrieular fluid pressure, and eonfluens sinuum pressure were monitored until death. The correlation coefficient between the latter two pressures was 0.873. Ventrieular fluid pressure was almost always a little higher than confluens sinuum pressure, the mean difference being i0 mm l-[g. For low pressures the ventricular fluid pressure recording appeared more sensitive; for high pressures the eonfluens sinuum pressure recording appeared superior, as the ventrieular eannula was often blocked by the walls of the lateral ventricle.Extrapolation from one form of intraeranial pressure to another should be avoided, as well as extrapolation from one species to another. Even individual differences between animals of the same species could sometimes be seen.A great many methods for measuring" and monitoring intracranial pressure have been developed though none are ideal. Perhaps the most common method is the one developed by Lundberg (Lundberg 1960) which is reliable and offers the possibility of ventricular injection and drainage at the same time, but even this method is not devoid of dangers (Sundb~rg et el. 1972). For animal experiments, extradural, snbdural and intracerebral balloons have been used, as well as a catheter in the cisterna magna or in one of the main venous sinuses.Simultaneous recordings of ventricular fluid pressure and venous sinus pressure have given extremely variable results. With raised ventricular fluid pressure in dogs, the sinus pressure has been reported