Plasma levels of dopamine (DA) and noradrenaline (NA) were measured in arterial and in femoral and renal venous blood of chloralose-anaesthetised dogs at rest, and during electrical stimulation of the femoral and renal sympathetic nerve supplies. In the femoral bed, sympathetic nerve stimulation elevated venous efflux of NA, but did not reproducibly elevate DA efflux: when this was increased, it comprised less than 1% of the stimulus-evoked catecholamine efflux. By contrast, renal nerve stimulation liberated both NA and DA from the kidney, and DA comprised about 8% of the total stimulus-evoked efflux. Comparison of efflux from intact and denervated kidneys indicated substantial neurogenic release of both NA and DA at rest, with DA comprising 20% of this efflux. The results extend previous evidence for dopaminergic sympathetic innervation of the dog kidney, and suggest that both dopaminergic and noradrenergic renal nerves are tonically active in anaesthetised animals.