The effect of a rapid reduction of plasma lipoproteins on the alpha-and gammd-tocopherol levels in plasma, erythrocytes, and platelets was studied. Sixteen successive plasma exchange procedures performed weekly in an adult with heterozygous familial hypercholesterolemia were evaluated. Plasma exchange was done by intermittent flow centrifugation, exchanging one plasma volume against a 4% human albumin solution. Plasma exchange reduced in plasma alpha-tocopherol from 41.5 t 8.9 to 23.6 t 4.8 pmol/L and gamma-tocopherol from 4.9 t 4.1 to 2.4 t 2.1 pmol/L, without changing their ratios to total lipids. It diminished alpha-tocopherol in platelets from 12.97 t 4.37 to 10.03 ? 1.78 pmol/10'3 cells and gamma-tocopherol from 1.43 t 0.55 to 1.06 k 0.41 pmol/ 10" cells, but did not affect erythrocyte tocopherols. The total amount removed per procedure was 47.57 5 13.65 pmol for alpha-tocopherol and 4.70 2 3.59 pmol for gamma-tocopherol. Plasma exchange increased the number of erythrocytes from 3.67 t 0.10.10'2 to 4.05 L 0.13.10'2 cells/L, without affecting their volume. Platelet count did not change, but mean platelet volume decreased from 7.7 t 0.5 to 6.9 ? 0.5 fl and platelet distribution width from 15.1 t 0.4 to 14.9 t 0.5. Thus, plasma exchange reduces plasma alpha-and gamma-tocopherol to the same extent as total lipids, and decreases these tocopherols in circulating platelets, along with a reduction in platelet size and, compared to the change in erythrocyte count, a fall of platelet number. The total amount of both tocopherols removed per procedure equals the recommended dietary allowances of 5-1 1 days for men and 7-14 days for women, assuming an effective absorption of 20-40%. This suggests the need for vitamin E supplementation during long-term plasma exchange treatment.