A monoclonal antibody raised against the mouse cerebellar inositol trisphosphate receptor was used to study the immunohistochemical localization of this protein in the human central nervous system. As in the brain of rodents, strong immunoreactivity was found in dendrites, axon and cell bodies of Purkinje cells, as well as in nerve endings in the cerebellar and vestibular nuclei. Cerebellar efferent fibres were the only positive structures demonstrated in the brainstem and no immunostaining could be detected in the spinal cord or dorsal root ganglia. By contrast, numerous immunoreactive neurons were present in several telencephalic and diencephalic structures, including the brain cortex, hippocampus, basal ganglia, basal forebrain, amygdala and thalamus. Immunostaining of these brain neurons was weaker than that found in Purkinje cells and was evident in cell bodies and dendrites. Thus, the human brain contains a molecule cross-reacting with the mouse inositol trisphosphate receptor protein that is expressed in a pattern similar to that found in rodents. These findings can be of great importance for understanding the function of this protein in normal brain and its modifications in neuropathological disorders.