There are conflicting reports regarding the effect of dietary cholesterol-oxidation products (oxysterols) on the development of atherosclerosis in experimental animals. To address this issue, apolipoprotein (Apo) E-deficient mice were fed a purified diet (AIN-93) or the same purified diet containing 0·2 g cholesterol or 0·2 g oxysterols/kg. The dietary oxysterols had no significant effect on the serum lipid levels. Although all of the diet-derived oxysterols (cholest-5-en-3β,7α-diol, cholest-5-en-3β,7β-diol, cholestan-5α,6α-epoxy-3β-ol, cholestan-5β,6β-epoxy-3β-ol, cholestan-3β, 5α, 6β-triol, cholest-5-en-3β-ol-7-one and cholest-5-en-3β, 25-diol) accumulated in the serum and liver, only cholest-5-en-3β-ol-7-one and cholestan-3β, 5α, 6β-triol accumulated significantly (P<0·05) in the aorta. The oxysterol diet did not result in elevation of the aortic cholesterol level or the lesion volume in the aortic valve. These present results indicate that exogenous oxysterols do not promote the development of atherosclerosis in ApoE-deficient mice.