Physiological studies are rapidly elucidating the function of the renal nerves; however, the anatomical location of the postganglionic cell bodies that supply the rat kidney has not been fully clarified. The origin of the sympathetic projection to the rat kidney was investigated in the present study by use of the fluorescent dye retrograde transport technique. Application of the dye to the renal nerves resulted in the fluorescent labeling of sympathetic cell bodies in paravertebral [thoracic (T) segment 6 through lumbar (L) segment 4] and prevertebral (renal, greater splanchnic, and celiac) ganglia and along the greater splanchnic nerve. Sympathetic neurons in all of these locations were found to fusiform in shape, 16-40 μm in diameter. They were dispersed uniformly throughout the paravertebral ganglia and splanchnic nerve, but in the celiac and greater splanchnic ganglia, cells projecting to the kidney were clustered near the origin of the renal nerve. In contrast to the cat, in which >50% of the renal sympathetic innervation arises from the prevertebral ganglia, in the rat the majority (>70%) of labeled renal sympathetic neurons were in the paravertebral ganglia, especially T12-L1. The distribution of renal sympathetic neurons in the paravertebral ganglia closely approximates the rostrocaudal distribution of renal afferent cell bodies in the dorsal root ganglia.