Electron transfer from iron or copper ions to oxygen is an important example of cellular free radical initiation. Oxygen-derived free radicals have been implicated as mediators of cellular injury in several model systems. To evaluate the importance of iron, copper, and zinc levels on lipid peroxidation in peritonitis, we measured peritoneum malondialdehyde (MDA) as a marker of lipid peroxidation, zinc, copper, and iron levels during an animal model of intraperitoneal sepsis. Additionally, the effects of free radical scavenger alpha-tocopherol administration were studied. The peritoneum MDA, iron, copper, and zinc levels were increased after induction of peritonitis with Escherichia coli. The treatment with alpha-tocopherol decreased peritoneum MDA, iron, and copper levels significantly but not the zinc levels. Additionally, the treatment with alpha-tocopherol 3 days prior to injection of E. coli decreased MDA, copper, and iron levels more than treatment with alpha-tocopherol at the time of injection of E. coli. Our results indicate that copper, iron, and zinc have important effects on peroxidation events in E. coli-induced peritonitis and that alpha-tocopherol treatment can improve the oxidant status. J. Trace Elem. Exp. Med. 15:79–84, 2002. © 2002 Wiley-Liss, Inc.