The aim of the study was to demonstrate the accumulation of b-amiloid and Tau in different clinical stages of Alzheimer's disease by using immunohistochemical methods. Primates, having Alzheimer's disease experimentally, were grouped into four clinical stages: Early confusion, late confusion, early demans and late demans. After perfusion of paraformaldehit %1/glutaraldehit %4, specimens from their cerebral cortex were embedded in paraffin. The sections were immunostained with anti-beta-amiloid and anti-Tau by using avidin-biotin-peroxidase staining technique. There was significant staining with beta-amiloid from the begining of the disease to the end. The method has demonstrated that senile plaques increase in number and size while the immunostaining becomes significantly intense according to the clinical stage of Alzheimer's disease. The immunoreactivity for Tau in senile plaques was quite similar in early stages and the staining intensity was lighter than the staining for b-amiloid. Immunostaining for "Tau" protein became more significant and senile plaques could be demonstrated at the late stage of demans. These results show that there is significant accumulation of beta-Amiloid from the beginning of Alzheimer's disease to the end; while Tau accumulation becomes more intense at the late stages of the disease. Immunohistochemical demonstration of beta-Amiloid might help to demonstrate the existence of senile plaques from the beginning of the disease while Tau can be detected at the later stages of Alzheimer's disease.