Normal weight (NW) and spontaneously intra-uterine growth-restricted newborn piglets (IUGR) were submitted to 1 hour hypoxia and hyperthermia followed by 3 hours reoxygenation. Glutathione (GSH, GSSG), lipid peroxidation products (TBAR) and cytochrome P450 dependent production of reactive oxygen species were studied by determination of H2O2 production and amplified chemiluminescence (CL) in brain and peripheral organs of NW and IUGR. A severe decrease of GSH was accompanied by enhanced H2O2 formation and lipid peroxidation in the brain of both NW and IUGR after hypoxia/hyperthermia and reoxygenation. In the other organs studied, only muscles showed enhanced lucigenine amplified CL and TBAR production. Nearly the same results in NW and IUGR reveal no higher risk of IUGR.