Activity of aldehide dehydrogenase (ALDH), alcohol dehydrogenase (ADH) in cytoplasmic fractions of brain structures (hypothalamus, midbrain, new cortex) and in blood serum as well as the content of noradreneline (NA) and dofamin (DA) in the mentioned structures and blood of rats preferring ethanol (PE) and rejecting ethanol (RE) has been investigated. ALDH isoforms have been revealed in rats preferring ethanol (PE) and these rejecting it (RE). The activity of the revealed forms of ALDH is higher in PE rats that in RE rats. PE and RE rats do not differ from one another as to ADH activity. It is shown that the NA content is decreased in PE rats and the DA level is increased in a number of brain structures and in blood as compared to RE rats.