Cessation of drug use in chronic opiate abusers produces a severe withdrawal syndrome that is highly aversive, and avoidance of withdrawal or associated stimuli is a major factor contributing to opiate abuse^,. Increased noradrenaline in the brain has long been implicated in opiate withdrawal, but it has not been clear which noradrenergic systems are involved. Here we show that microinjection of β-noradrenergic-receptor antagonists, or of an α2-receptor agonist, into the bed nucleus of the stria terminalis (BNST) in rats markedly attenuates opiate-withdrawal-induced conditioned place aversion. Immunohistochemical studies revealed that numerous BNST-projecting cells in the A1 and A2 noradrenergic cell groups of the caudal medulla were activated during withdrawal. Lesion of these ascending medullary projections also greatly reduced opiate-withdrawal-induced place aversion, whereas lesion of locus coeruleus noradrenergic projections had no effect on opiate-withdrawal behaviour. We conclude that noradrenergic inputs to the BNST from the caudal medulla are critically involved in the aversiveness of opiate withdrawal.