In obstructive jaundice, postoperative complications are related to gut-derived endotoxemia and possibly mediated by cytokines such as tumor necrosis factor (TNF) and interleukin-6 (IL-6). This study investigated the course of IL-6 and TNF after surgery in bile duct-ligated rats (BDL) treated with and without an enteral endotoxin binder (cholestyramine). Endotoxin in rat plasma was determined by blocking cytokine production in whole blood cell cultures stimulated by rat plasma using antibodies directed against the endotoxin (CD14) receptor. Surgery elicited a significant IL-6 response in saline-treated BDL rats (BDL-SAL). TNF, however, remained at its low preoperative levels. Cholestyramine treatment resulted in undetectable preoperative TNF and IL-6 levels, but levels of both cytokines were significantly raised after surgery. Endotoxin, as determined by the CD14 blockade test, was identified in the BDL-SAL group, before (time 0) and after surgery (2 and 4 h), whereas in the cholestyramine group endotoxin was only present at 2 h after surgery. The lack of a postoperative plasma TNF response in the BDL-SAL group in the continuous presence of endotoxin suggests endotoxin tolerance for TNF production in obstructive jaundice.