Somatostatin contents of striatum, hippocampus, and pons medulla have been followed in two inbred strains of mice (C57B1/6J and Balb/cJ) with aging and long term alcohol exposure (over a 25 month period of intoxication). Marked strain dependent differences in basic levels of somatostatin and genotypic variations in reactivity of this neuropeptide to aging processes and chronic alcohol exposure were demonstrated. The Balb/c strain exhibits a significant age dependent decrease in striatal and hippocampal somatostatin levels whereas the C57B1 mice remain unchanged until the 27 month. Moreover, only the Balb/c strain reacts to chronic alcohol exposure, showing a significant increase in somatostatin levels in those structures affected by the aging process. Such genotypic differences may be involved in man in specific pathologies in aged individuals and in alcohol induced behavioral alterations in alcoholics.