Acute septic shock is one of inflammatory diseases mediated by pro-inflammatory cytokines such as tumor necrosis factor (TNF)-${alpha}$. In this study, we examined the pathological difference and mechanism of lipopolysaccharides isolated from E. coli (E-LPS) or S. abortus (S-LPS) on inducing acute septic shock in ICR mouse. All mice were died by intraperitoneal treatment of S-LPS with 0.75 mg/kg, whereas E-LPS treated with even 3 mg/kg only showed 30% of mice lethal, indicating that S-LPS may be more feasible in triggering a strong septic shock condition. The secretion pattern of TNF-${alpha}$, a critical pro-inflammatory cytokine in septic shock condition, was also distinct between E-LPS- and S-LPS-treated groups. Thus, S-LPS strikingly increased serum level of TNF-${alpha}$ (6 ng/ml) at 1 h, while E-LPS just displayed at 2 ng/ml level. However the interaction of S-LPS with LPS receptor toll like receptor (TLR)-4, was not stronger than that of E-LPS, according to experiments with macrophage cell line RAW264.7 cells. Thus, E-LPS rather than S-LPS strongly enhanced the production of TNF-${alpha}$. Interestingly, S-LPS more strongly up-regulated splenocyte proliferation, compared to E-LPS group, whereas there was no difference between S- or E-LPS treated groups in proliferation of Balb/c- or C57BL/6-originated splenic lymphocytes. Therefore, our data suggest that S-LPS is a more active endotoxin and that the strong septic shock-inducing effect of S-LPS seems due to the enhancement of early TNF-${alpha}$ production and S-LPS-sensitive lymphocyte proliferation.