The immunocytochemistry of Tau proteins in the cortical pyramidal neurons of the adult microcebes has been studied, using antibodies against human normal and pathological Tau proteins. Some changes related to the age and to some pathologies were observed. In fact, during the adult life, Tau proteins appeared as very thin granulations scattered in the whole neuronal cytoplasm. With age, a part of these proteins aggregated and became like thick granules at the neuron periphery; the distribution was not uniform, and numerous neurons with aggregated Tau proteins were observed in amyloid plaque-containing brains. Abnormally phosphorylated Tau proteins were also observed in some aged animals, using an absorbed anti-PHF recognizing the pathological Tau proteins characteristic of Alzheimer's disease. This present work confirms that the microcebe is a good model for studying disfunctions involved in the normal cerebral aging and in some neurodegenerative disorders which affect humans.