The effects of a diet containing soybean oil (SBO), rice bran oil (RBO), palm oil (PO) or a RBO/PO (3:1) mixture on the composition and oxidation of small dense low-density lipoproteins (sdLDL) in 16 hypercholesterolaemic women were investigated. During the 8-week control period, participants consumed a free-choice weight-maintaining diet comprising carbohydrate (55% energy), protein (15% energy) and fat (30% energy) with < 300 mg/day of cholesterol. During each 10-week study period, participants consumed this same diet but with the addition of one of the three test oils or the RBO/PO mixture. Total cholesterol and low-density lipoprotein (LDL)-cholesterol levels were significantly reduced during SBO, RBO and RBO/PO consumption, while high-density lipoprotein cholesterol was significantly decreased by SBO consumption. There was a significant reduction in sdLDL-cholesterol levels only after using SBO and it tended to be reduced during RBO/PO consumption, whereas it was significantly increased following PO consumption. The sdLDL oxidation lag time was significantly increased during PO, RBO/PO and RBO consumption, but significantly reduced following SBO. The results for the RBO/PO mixture suggest that this oil mixture might further reduce the risk of atherosclerosis.