Enzymatic histamine synthesis by renal glomeruli of the rat has been examined. Assays of the partially purified enzyme demonstrated a pH optimum of 6.2, a Michaelis-Menten constant of 2.4 X 10(-4) histidine, and lack of potentiation by benzene. These data thus indicate that renal glomeruli contain the histidine-specific histidine decarboxylase.