Serial sections of human thalami, cut in the 3 standard planes, were stained in alternating series for Nissl substance, myelin, cytochrome oxidase and acetylcholinesterase. Nissl and acetylcholinesterase-stained sections revealed a parcellation of the nuclei that could be correlated with that used in the macaque monkey thalamus. Human nuclei were accordingly re-named using the monkey nomenclature. Apart from differences of size, the nuclei of the human and monkey thalamus are remarkably similar. In the human ventral nuclear complex there is a very clear histochemical distinction between nuclei which, on the basis of comparison with the monkey, probably form the pallidal, cerebellar and lemniscal relays to premotor, motor and somatic sensory cortex, respectively. In the human somatic sensory relay nucleus there is a further clear cytoarchitectonic distinction between components that are probably equivalent to the relays for deep and cutaneous receptors in the equivalent monkey nucleus.