Myocardial necrosis was induced experimentally by the method of Rona, and coenzyme Q(9) and α-tocopherol concentrations were measured in the serum and lipoprotein fractions. There was no significant change in the serum coenzyme Q(9) concentrations after isoproterenol administration. In contrast, the serum α-tocopherol levels decreased 6h and 12h after the administration, and the α-tocopherol-cholesterol ratio decreased within 12h. In control subjects, most of coenzyme Q(9) was distributed in the VLDL and LDL fractions, while most of α-tocopherol was present in the HDL fraction. The coenzyme Q(9) levels decreased 6h, 12h and 24h after isoproterenol administration in VLDL, and the lowest level was at 12h. On the other hand, the coenzyme Q(9) level elevated within 12h in the LDL fraction. The α-tocopherol level decreased rapidly in the VLDL fraction, reaching a minimum within 6h, and showed an increase at 12h in the LDL fraction. There was no significant change in the HDL fraction. The coenzyme Q(9)-cholesterol ratio increased within 12h in the LDL fraction and within 6h in the HDL fraction. The α-tocopherol-cholesterol ratio decreased within 6h in the VLDL and HDL fractions, while there was no significant change in the LDL fraction. The coenzyme Q(9)-α-tocopherol ratio increased within 6h in the VLDL and HDL fractions and within 12h in the serum and LDL fraction. These results indicate that the metabolism of coenzyme Q(9) is different from that of α-tocopherol in lipoproteins. It is concluded that coenzyme Q is mainly transported from VLDL (and chylomicron) to LDL at the onset of acute vascular accidents, for the lipase activity is stimulated by hormones, and then coenzyme Q is carried from LDL and HDL to mitochondria rich organs through the LDL receptor or other routes.