The first step in ethanol metabolism is carried out by two enzyme systems: Alcohol dehydrogenase and cytochrome P-450. The cytochrome P-450 system also detoxifies a wide variety of foreign compounds. On the basis of recent evidence, metabolic reasons are suggested for four well-known consequences of alcoholism: (a) The development of fatty liver; (b) the development of metabolic tolerance; (c) the occurrence of interactions between drugs and alcohol; and (d) the fact that many of the kilocalories attributable to ethanol do not seem to "count "count "count" when ethanol forms a major part of the diet.