This study examined the levels of serum tumor necrosis factor (TNF), interleukin-1 (IL-1) and plasma cortisol levels in adult cows after intravenous administration of lipopolysaccharide (LPS) extracted from Escherichia coli. The adult cows exhibited clinical signs of endotoxic shock. The mean concentrations of serum TNF was 557.9 U/ml and serum IL-1 was 90.6 U/ml at 2 hr after LPS administration following severe endotoxic shock. Plasma cortisol concentrations increased immediately and a peak level was 131.4 ng/ml at 1 hr after LPS challenge. These results suggested that circulating concentrations of TNF, IL-1, and cortisol may be associated with clinical signs of endotoxemia in adult cows.