Renal catecholamine metabolism encompasses: (1) catecholamine metabolism within the kidney intrinsic to renal sympathetic nervous function and renal tubular production of dopamine; (2) the overflow of catecholamines, released within the kidney, into the renal vein; (3) the excretion into urine of catecholamines and catecholamine metabolites, and (4) the extraction of catecholamines from plasma by the kidney. Study of these elements of catecholamine metabolism by the kidney provides a theoretical underpinning for the use of biochemical methodology in the experimental and clinical investigation of the properties of the renal sympathetic nerves.