Obstructive jaundice is associated with a predisposition to systemic hypotension and acute renal failure. Altered vascular reactivity may contribute to the development of hypotension. In this experimental study on dogs, alterations in vascular contractile responses to noradrenaline, serotonin and KCI were investigated. Contractile responses to noradrenaline, serotonin,,, KCI and relaxation responses to papaverin and acetylcholine were provoked in isolated femoral arteries of both control dogs and animals with obstructive jaundice. In this situation concentration-response curves of noradrenaline and serotonin were blunted when compared with controls. This blunting disappeared when endothelium was removed. In rings precontracted with phenylephrine, EDRF relaxation responses to acetylcholine were increased significantly as compared to controls; at lower concentrations maximal relaxation response occured. Contractile responses to KCI and relaxation responses to papaverin did not differ between the groups, endothelium present or removed.