Using histochemical and immunohistochemical techniques, distribution of activity of oxidative mitochondrial enzyme cytochrome oxidase (CO) and calcium-binding proteins-immunoreactivity was studied in the spiral ganglion and auditory nuclei of brainstem in two turtle species. Calbindin-, parvalbumin-and calretinin-immunoreactivity in neurons and neuropil of cochlear, supraolivary complexes, the lateral lemniscal nucleus and neuropil of spiral ganglion is shown to coincide topographically with high activity of CO. Similarity of the studied metabolic and neuro-chemical characteristics of these auditory centers in reptiles, birds and mammals suggests some general principles of their organization in amniotes, despite phylogenetic differences and peculiarities of auditory system in different species.