SUMMARY1. Utilizing a mono‐specific antiserum produced in rabbits to hog kidney aromaticl‐amino acid decarboxylase (AADC), the enzyme was localized in rat kidney by immunoperoxidase staining.2. AADC was located predominantly in the proximal convoluted tubules; there was also weak staining in the distal convoluted tubules and collecting ducts.3. An increase in dietary potassium or sodium intake produced no change in density or distribution of AADC staining in kidney.4. An assay of AADC enzyme activity showed no difference in cortex or medulla with chronic potassium loading.5. A change in distribution or activity of renal AADC does not explain the postulated dopaminergic modulation of renal function that occurs with potassium or sodium load