Free radicals are likely involved in the aging process and there is a growing body of evidence that free radical damage to cellular function is associated with a number of age-related diseases such as atherosclerosis, cancer, and neurologic disorders. The present study was designed to evaluate in a healthy population the evolution with age of 8-epiPGF2alpha plasma levels, a recently proposed marker of in vivo lipid peroxidation. Moreover we investigated this marker of oxidative stress in patients with Alzheimer's disease (AD), an age-related neurodegenerative disorder in the development of which free radicals have been involved. Our results show that in the healthy population studied, despite decreased antioxidant defenses with increasing age as monitored by antioxidant capacity measurement, plasma 8-epiPGF2alpha levels were not correlated with age. Moreover, we have demonstrated that AD patients presented no modification of plasma 8-epiPGF2alpha level and no major alteration of the antioxidant status. In conclusion, the measurement of plasma 8-epiPGF2alpha did not allow us to detect alterations in oxidative stress with aging or in AD.