The uptake and metabolism of long chain fatty acids in isolated mucosal cells from chicken small intestine are studied. The viability of the isolated enterocytes is proven by linear oxygen consumption, C02 and lactate formation from glucose and the active transport of glucose. The transport of palmitic and oleic acid is mediated by passive diffusion. This is demonstrated by the following results: (1) no saturation kinetics in the concentration range of 0.1 -10.0 mM; (2) no competitive inhibition of the uptake by structurally related compounds; (3) no influence of 2,4-DNP and cyanide of the uptake; (4) the uptake is independent of sodium ions. Uptake rates of palmitic and oleic acid from suspensions are significantly higher than from the corresponding fatty acid-bovine serum albumin complexes. In both cases the uptake of palmitic acid proceeds faster than the uptake of oleic acid. Palmitic acid is oxidized to C02 and incorporated into glycerides by enterocytes. Glucose serves as a glyceride-glycerol precursor. Its addition decreases the oxidation of the fatty acids and enhances glyceride synthesis markedly. Free glycerol is phosphorylated by enterocytes and can also serve as a glyceride-glycerol precursor.