To investigate the effects of acute fecal peritonitis on plasma and tissue lipid peroxidation and possible protective effects of vitamin E (Vit E) and cimetidine at 4 h in a rat peritonitis model, four groups were designated as: controls, peritonitis, Vit E and cimetidine. Plasma, liver, lung and kidney thiobarbituric acid reactive substances (TBARS) and conjugated diene (CD) levels were measured to monitor oxidative injury. The present fecal peritonitis model caused a significant elevation in liver TBARS; however, neither Vit E nor cimetidine was effective in preventing TBARS formation. Administration of Vit E and cimetidine caused significant decrements from the peritonitis value in liver and lung CD levels.