The purpose of this study was to observe the effects of dietary intervention, through the modification of dietary fatty acids composition and antioxidant vitamins, on plasma thromboxane B (TXB) levels in postmenopausal women with hypercholesterolemia. The subjects were treated for 12 weeks with one of three methods: hormone replacement therapy (HRT group, n=8), dietary intervention (DIET group, n=8), or HRT combined with dietary intervention (HRT +DIET group, n=8). Changes in serum phospholipid fatty acids composition, serum peroxides, and plasma TXB levels were measured at weeks 0, 4 and 12. The P/S ratio increased and the n-6/ n-3 ratio decreased in the DIET and the HRT +DIET group at week 4 (p<0.05). The ratio of C20:5/C20:4 in serum phospholipid increased in the DIET (p<0.05) and the HRT +DIET groups (NS) at week 4. Plasma TXB levels decreased in the DIET (-35%, p<0.05) and the HRT +DIET groups (-18.8%, NS) at week 4. Serum lipid peroxides levels significantly decreased by 10.5% and 15.2% in the DIET group at weeks 4 and 12, and by 10.8% in the HRT +DIET group only at week 12 (p<0.05). Dietary intervention may lower thrombotic risks in Korean postmenopausal women by changing the serum fatty acid composition, serum lipid peroxides levels and plasma thromboxane B levels.