The intestinal absorption of labeled folic acid ([3H]pteroylmonoglutamate) was determined from urinary and fecal recoveries of tritium in pairs of monkeys fed control liquid diets or diets containing 50% of energy as ethanol for a 24-mo period. Weight gain, fecal fat excretion, nitrogen balance, D-xylose absorption, serum folate levels, jejunal histology, and intestinal enzyme activities were similar in each group. Liver biopsies obtained after 12 and 24 mo of feeding demonstrated steatosis and megamitochondria in the ethanol-fed group, with decreased hepatic levels of folate at 24 mo. Intestinal malabsorption of labeled folic acid in the ethanol-fed monkeys was indicated by decreased urinary recovery of tritium but increased fecal recovery of tritium after intragastric administration of [3H]pteroylmonoglutamate. These studies suggest that folic acid malabsorption follows the chronic administration of ethanol together with a nutritious diet.