The effects of vitamin C and/or E deficiency on lipoprotein metabolism were investigated in the inherently scorbutic Osteogenic Disorder Shionogi (ODS) rat. In the vitamin C-deficient (C-def) group, marked increases in plasma VLDL and LDL cholesterol were observed (by comparison with the vitamins C- and E-sufficient control group). In rats kept deficient in both vitamin C and vitamin E (C,E-def), LDL cholesterol was significantly higher than in the C-def group even though the levels of VLDL and HDL cholesterol were similar between the two groups. TBARS values for the LDL fraction in the C-def group were of the same magnitude as in the E-def group, and these values were significantly higher than those obtained for the control group. In the C,E-def group, the values were even higher than in the E-def and C-def groups. The nondenatured PAGE of the LDL fraction indicated the appearance of HDLc in the C-def and C,E-def groups. The SDS-PAGE of the LDL fraction showed increased apo B-48 in the C-def and C,E-def groups and increased apo E in the C,E-def group. Decreased plasma LCAT activity in the E-def, C-def, and C,E-def groups indicated an alteration in HDL metabolism as a result of oxidation. These results suggest that lipid peroxidation and some distinct features of lipoprotein metabolism resulting from vitamin C deficiency become more significant when vitamin E is also deficient along with vitamin C deficiency.