Background: The oxidative modification of LDL is believed to be an initial step in atherosclerosis. Thus, antioxidative substances such as carotenoids may have a role in the prevention of coronary heart disease. We examined the susceptibility of LDL to Cu2+ oxidation in young adults before and after a single dose of β-cryptoxanthin. Methods: 1.3 mg of β-cryptoxanthin was administered to 12 apparently healthy young volunteers. Six of the volunteers received esters, the other six free β-cryptoxanthin. The plasma concentration of β-cryptoxanthin and the susceptibility of LDL to copper-induced oxidation ex vivo in terms of the duration of lag time were measured before and 12 h after β-cryptoxanthin ingestion. Results: A single dose of β-cryptoxanthin significantly increased the mean plasma β-cryptoxanthin concentration and the mean cholesterol adjusted β-cryptoxanthin concentration by 117 and 133%, respectively. No effect on the length of lag time was assessed. However, in LDL isolated from plasma 12 h after β-cryptoxanthin administration the lengths of lag time correlated significantly with the plasma β-cryptoxanthin concentration and with the cholesterol adjusted β-cryptoxanthin levels. The lag time did not differ significantly between volunteers who received esters and those who received the same dosage as free β-cryptoxanthin. At both measuring points, smokers, male volunteers and women using oral contraceptives tended to exhibit lower β-cryptoxanthin concentrations and lower cholesterol adjusted β-cryptoxanthin concentrations as well as increased LDL oxidizability compared to nonsmokers and women not using oral contraceptives. Conclusion: A single dose of β-cryptoxanthin does not enhance the duration of LDL lag time ex vivo in healthy young subjects. Copyright © 2004 S. Karger AG, Basel.