Concentrations of albumin and nonesterified fatty acids (FAs) have been determined in bovine serum and aqueous humor (AH) with regard to the FA-to-albumin molar ratio, which has been proved decisive for the FA cytotoxicity to bovine lens epithelial cells as described previously. In 6- to 7-month-old female calves the average albumin level was reduced 309-fold from 638 µmol/l in serum to 2.00 µmol/l in AH, in 72- to 84-month-old cows 405-fold from 632 to 1.56 µmol/l, and in 12- to 18-month-old bulls 395-fold from 553 to 1.40 µmol/l. In 64% of the animals the albumin concentration in AH differed significantly between both eyes. The serum albumin values resulted in a Gaussian curve, but the frequency distribution for AH albumin values skewed to the right. Using an enzymatic method the concentrations of nonesterified FAs were determined in serum as well as in concentrated AH samples. In all animals investigated the molar FA-to-albumin ratio was higher in AH than in serum. The results are discussed in view of the assumption that unsaturated nonesterified FAs might be cataractogenic risk factors.