S planchnic metabolism was studied to quantify changes underlying the fatty liver, hyperlipemia, and hypoglycemia produced by ethanol. Four subjects fasted for 15 h were compared with five subjects fasted for 69 h under basal conditions and during continuous intravenous infusion of sufficient ethanol to give a concentration of 3-5 mM in arterial blood plasma. Splanchnic storage of fatty acids was estimated from the difference between uptake of FFA and secretion of derived products. Basal values for splanchnic uptake of FFA were twofold higher after the 69-h fast while splanchnic storage of fatty acids and production of ketone bodies increased threefold. Values for basal secreation into the blood of triglycerides derived from FFA were similar in the two groups. In both nutritional states, the fraction of FFA taken up in the splanchnic region oxidized to ketone bodies and to CO2 fell when ethanol was given because of preferential oxidation of ethanol to acetate, and the fraction esterified rose. However, systemic transport and splanchnic uptake of FFA fell with ethanol in subjects fasted 15 h, so that neither storage of triglycerides in splanchnic tissues nor secretion into the blood increased. In subjects fasted 69 h, ethanol increased transport of FFA and splanchnic storage of fat. In all but one subject it also increased secretion of triglycerides into the blood. The concentration of glucose in blood fell during ethanol infusion in all five subjects undergoing the 69-h fast. Mean splanchnic glucose production was maintained at about one-half of the pre-ethanol value, despite virtual cessation of splanchnic uptake of lactate and of those amino acids that are metabolized via malate. Quantitative estimates of extrasplanchnic metabolism suggest that enhanced formation of alpha-glycerophosphate from glucose, in addition to impaired hepatic gluconeogenesis, may contribute to ethanol-induced hypoglycemia in man.