Four kinds of lipoproteins contained in human diabetic cataract lens were separated by of sequential flotation in an ultracentrifuge, and the quantities of each were determined by selective precipitation. Chylomicron, very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL) were separated from cataract lenses as lipoprotein fractions, and quantified. Chylomicron was present in the largest quantity among the four. There was no significant difference between the total amount of lipoprotein contained in diabetic cataract lenses (96.95 +/- 4.03 micrograms/lens) and that in senile cataract lenses (89.51 +/- 8.35 micrograms/lens). The quantities of VLDL and LDL, however, were significantly larger in diabetic cataract lenses (14.84 +/- 0.55 and 20.97 +/- 0.58 micrograms/lens, respectively) than in senile cataract lenses (6.30 +/- 0.46 and 7.45 +/- 0.61 micrograms/lens, respectively). We demonstrated histologically that LDL receptors are localized on the lens epithelium and its underlying layer.