Induction of endotoxin tolerance in rats led to reductions in bile flow and BSP excretion. BSP serum retention or storage of BSP in the liver was not affected. Although serum alanine aminotransferase (ALT) activity was slightly elevated in endotoxin-tolerant rats, the levels of serum aspartate amino-transferase (AST) and hepatic 5'-nucleotidase were normal. These in vivo data support the validity of in vitro studies demonstrating the cholestatic effect of endotoxin and the viewpoint that endotoxin may be responsible for the cholestatic jaundice associated with Gram-negative bacterial infections.