The free radical-mediated oxidation of biological molecules and its inhibition by antioxidant have been the subjects of extensive studies in relation to oxidative damage and disorders in vivo. Various methods have been applied to measure oxidative events and also antioxidant action in vitro and in vivo. One of the popular approaches involves the use of fluorogenic probes. We have elucidated the oxidation mechanism of biological samples especially lipoproteins using these probes and also studied to find out the specific oxidative marker. Our final goal is to realize high QOL for human kinds by determining the stress marker and enhancing defense capacity toward disorders.