ABSTRACT:The water‐soluble proteins of the cerebral gray matter and some enzyme systems (cholinesterase, acetylcholinesterase, lactate dehydrogenase, malate dehydrogenase, acid phosphatase) were studied in 9 autopsy cases of Alzheimer's presenile or senile dementia, 1 case of Pick's disease and 1 case of cerebral arteriosclerosis. The proteins and enzyme patterns were visualized on polyacrylamide gradient gels after electrophoresis. In all patients studied, the profiles of cerebral gray‐matter proteins were normal. In the patients with advanced dementia, the enzyme patterns usually were abnormal. Particularly in Alzheimer's disease, the activity of malate dehydrogenase was markedly increa