This study evaluates the hypotensive properties and the mechanism of action of the aqueous leaf extract of Leonotis Leonurus in anesthetized male Wistar rats, using computerized blood pressure recording system. The effect of aqueous leaf extract of L. leonurus on the blood pressure was investigated by infusing intravenous doses of 200 mg/kg to 1g/kg into anesthetized rats. Its underlying blood pressure lowering mechanism was also studied by challenging the parasympathetic, sympathetic and muscarinic systems of anesthetized rats by pretreating with, dobutamine, atenolol, and atropine. Pretreating the animals with reserpine and L. leonurus was also employed in order to challenge the adrenal system of rats. The results showed that the aqueous leaf extract of Leonotis leonurus produces a dose dependent fall in the systolic blood pressure, diastolic blood pressure and heart rate of the rats. This effect on heart rate may suggest the involvement of ?- adrenergic receptors in the cardiac effect of L. leonurus.