Background: Neurotrophin -4(NT-4) plays an important role in the development and maturity of nerve system, which not only has certain adjustment reactions in the survival, proliferation and differentiation of some specific subgroup neurons, and the plasticity of neurite, but also a necessity to the existence of some neurons. However, most of the data were from experiments in vitro and its mechanism in vivo is still not well established, and the reports about the distribution of NT-4 in vivo could hardly be seen as well. There was no such report about the research in advanced Primates, monkey brain. Objective: To discuss the distribution of NT-4 in the brain of adult Primates animal, monkey, and to provide an useful morphological gist for further researches in NT-4 as well as its relationship with the functions of mature central nerve system. Design: A case-control study with PBS instead of primary antibody. Setting and Materials: The study was completed in the Laboratory of Neurological Science of Kunmin Medical University. Animals were 7 adult male rhesus obtained from Kunmin Animal Institution of China Scientific Academy with a mean body weight of 6 kg. Methods: Ketamine was injected into muscles for anesthesia, and Zamboin's solution was used in cardiac perfusion for fixation. Each part of cerebral tissue was taken for frozen sections with a thickness of 25 μm. Immunohistochemical technique SP method was introduced. Antibody was anti-rabbit NT-4 polyclonal antibody. Main Outcome Measures: NT-4 immunoreactive(IR) positive substances(in brown rosary, thread or granule shapes) in different sites of the brain were observed under optical microscope. Control study: 0.05 mol/L of PBS was used to replace the primary antibody for immunohistochemical staining. Results: NT-4-IR distributes on some neuron somas and umbos in cerebral cortex III to V layer as well as a few of gliocytes in white substance, some neurons in cerebellar cortex and white substance, some neurons in hippocampal CA1, CA2 and CA3 regions. Besides, scattered IR positive cell and intertexture fibres could be seen at lenticular nucleus, caudate nucleus, pontine nucleus, vestibular nucleus, cuneate nucleus, gracile nucleus and accessory nucleus. Conclusion: NT-4-IR widely distributes in multiple tissues and cells in the brain of rhesus, which suggests its function might be related to different types of neurons and some non-neurons as well.