AbstractBoth reserpine and benzquinamide were capable pf impairing thein vitrouptake of C14‐adrenaline by bovine and rabbit adreno‐medullary granules, however, they differed markedly in their relative potency. Thein vivostudies using mice and thein vivo—in vitrostudies employing rabbits indicated that the time course of granular blockade after reserpine and benzquinamide injections also differed. Benzquinamide was shorter‐acting and less potent than was reserpine. Subcellular distribution studies indicated that while both drugs could impair the invivouptake of3H‐α‐methyl noradrenaline, only reserpine administration resulted in both an increase in the amount of3H‐α‐methyl noradrenaline found in the supernatant fraction and an increase in the amount of3H‐α‐methyl normetanephrine recovered from the whole heart. It is concluded that while reserpine and benzquinamide have many qualitatively similar effects on amine uptake and depletion, differences in their actions on the subcellular