PH determinations by means of a sturdy, spear-electrode inserted in the cerebellar tissue immediately after necropsy were carried out in 60 patients suffering from different disorders and dying in hospital, and from 25 individuals killed instantly by violent accidents. A correlation was found between the presence of NGL and low pH levels in the cerebellum (average pH 5.56); subjects without NGL changes showed an average pH OF 6.08. No correlation was found between the pH levels and the time after death, or between pH and any specific disease. The so-called acute selective necrosis of the granular layer of the human cerebellar cortex (NGL), is considered from the present studies to be a phenomenon of postmortem origin. Its relationship to certain specific diseases can be explained by the fact that in these conditions there is a higher postmortem acidity, known to promote autolysis.