There are still controversies concerning the concept and diagnosis of multiple systems organ failure (MSOF), since the term does not precisely define its true nature, and its differential diagnosis with other irrelevant clinical conditions, such as senile dysfunction of organs, agonal state, etc, remains unclarified. Our studies on both human burn patients and rat model by means of electron spin resonance (ESR) showed that there was an excessive generation of free oxygen radicals resulting in lipid peroxidation of cell membrane of various tissues. The intestine seemed to be particularly sensitive to hypoperfusion-reperfusion injury, as diamine oxidase activity of the ileum was lowered and translocation of bacteria occurred, indicating failure of intestinal mucosal barrier function. Concomitant determinations of plasma endotoxin (LPS) and tumor necrosis factor alpha (TNFa) levels showed significant elevation, especially in patients who finally developed MSOF. The data suggested that intestinally derived b There are still controversies concerning the concept and diagnosis of multiple systems organ failure (MSOF), since the term does not precisely define its true nature, and its differential diagnosis with other irrelevant clinical conditions, such as senile dysfunction of organs, agonal state, etc , remains unclarified. Our studies on both human burn patients and rat models by means of electron spin resonance (ESR) showed that there was an excessive generation of free oxygen radicals that in lipid peroxidation of cell membrane of various tissues. The intestine seemed to be Particularly sensitive to hypoperfusion-reperfusion injury, as diamine oxidase activity of the ileum was lowered and translocation of bacteria occurred, indicating failure of intestinal mucosal barrier function. Concomitant determinations of plasma endotoxin (LPS) and tumor necrosis factor alpha (TNFa) levels showed significant elevation, especially in patients who finally developed MSOF. The data suggested that int estinally derived b