The origin of dopamine (DA) and its metabolite in predominantly noradrenergic brain areas was investigated in rats with a unilateral electrolytic lesion of the locus coeruleus. Using the unlesioned side as a control, levels of DA, noradrenaline (NA), and the DA metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were measured in lateral hippocampus, cerebellum, frontal cortex, occipital cortex, brainstem and striatum. Lesion of the locus coeruleus decreased brain NA levels in those regions innervated by this nucleus, but had no effect on levels of DA and DOPAC in any of the regions studied. It is concluded that even in regions of very low DA concentration, DA and DOPAC probably originate from dopaminergic neurons rather than via NA formation in noradrenergic neurons.