We used the retrograde transneuronal transport of a neurotropic virus, pseudorabies virus (PRV), to identify the neurons in sympathetic ganglia, spinal cord and brain which regulate renal function and renal circulation. PRV was microinjected into the left kidney of 70, pentobarbital-anesthetized, male rats. After an incubation period of 1-4 days, rats were anesthetized and sacrificed. PRV-infected neurons were located immunocytochemically in pre- and paravertebral sympathetic ganglia, the intermediolateral cell column of the T10-T13 segments and several brainstem cell groups: the medullary raphe nuclei, rostral ventrolateral medulla, rostral ventromedial medulla, A5 cell group, and the paraventricular hypothalamic nucleus. In more heavily infected rats, additional labeling was found in the locus coeruleus, periaqueductal gray matter, lateral hypothalamic area, zona incerta, and anterior hypothalamic area. No infected propriospinal neurons were observed in the lateral spinal nucleus or gray matter of the caudal cervical, lumbosacral or thoracic spinal segments not containing infected putative sympathetic preganglionic neurons. The paucity of infected propriospinal neurons in the presence of infected brainstem neurons, even in lightly infected rats, is discussed in reference to the relative importance of descending vs spinal regulation of the sympathetic outflow to the kidney.