1. Atropine has recently been known to possess a sympathetic ganglion blocking effect. If atropine blocks the sympathetic ganglia innervating the blood vessels, the drug should cause depressor responses. The author attempted to verify this assumption in urethane-anesthetized rabbits having atropinesterase. 2. Ten and 50μg/kg of atropine produced little variation of the blood pressure; 250μg/kg slight depressor responses; 1,250μg/kg distinct ones. Under hexamethonium-infusion, 10 and 50μg/kg produced observable depressor responses; 250 and 1,250μg/kg produced more pronounced ones. 3. In experiments examining influence of phenoxybenzamine and bretylium on the atropine responses, the lowered blood pressure by these agents was raised by simultaneous infusion of angiotensin with hexamethonium. The depressor responses to atropine (10, 50 and 250μg/kg) were slight after the administration of phenoxybenzamine and bretylium. 4. Propranolol did not affect the depressor responses to atropine. 5. In spinalized rabbits the lowered blood pressure was raised by the angiotensin-infusion. In these animals receiving the simultaneous hexamethonium-infusion, atropine (10, 50 and 250μg/kg) produced little depressor responses. 6. From these results it is inferred that atropine produced the depressor responses by blocking the sympathetic ganglia innervating the blood vessels.