The paper deals with a detailed histochemical mapping of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in the diencephalon and mesencephalon of Uromastix hardwickii. In AChE in contrast to BChE preparations, most of the nuclei reveal intense activity Interestingly, the hypothalamic nuclei demonstrate positive reactions to AChE but totally negative reactions in BChE preparations. The enzymatic activity in fiber tracts is totally negative for AChE; on the contrary, it is intensely positive for BChE. Neurosecretory substance, in the hypothalamic region, is positive for the two preparations of the enzymes. The role of these enzymes, as related to the functional activities of the various nuclei and fiber tracts, has also been discussed.