The effect of glucan (lentinan), beta(1----3)-glucan derived from Lentinus edodes, was evaluated in a clinically relevant septic model. Male, Japanese, white rabbits were intravenously injected with lentinan (1 mg/body) just before septic insult, induced by injecting fecal suspension into the ligated choledochus. In septic animals without lentinan treatment, platelet counts dropped serially following the septic insult and a paracoagulation test, measured by protamine gelation, turned positive. Plasma bilirubin and creatinine elevated significantly in comparison with control animals injected with saline, at 9 h and at 6 and 9 h. respectively. In lentinan-treated septic animals, platelet counts did not decrease and a significant difference was found at 9 h, compared to the untreated septic animals. The degree of positive paracoagulation was less prominent. The elevation of plasma bilirubin and creatinine levels was also less prominent and a significant difference was found at 9 h. Plasma endotoxin elevated significantly at 9 h in the untreated septic animals in comparison with lentinan-treated septic and control animals. The findings suggest a modification of the septic processes by the administration of glucan.