The range of the Na+, K(+)-ATPase functional stability in microsomal fraction of rat brain cortex under long-term chronic ethanol (15%, v/v) consumption was ascertained. The enzyme activity decreased only after 15 months of alcoholisation on the background of the stable structural membrane characteristics (on the basis of the intrinsic and 1-anilinonaphthalene-8-sulfonate fluorescence parameters) and SH-content in postmitochondrial supernatant. The cellular homeostatic mechanisms under ethanol effect are discussed.