Abstract: The effect of the aqueous extract of the leaves of Stachytarpheta jamaicensis (L.) Vahl. on blood pressure was investigated in anaesthetized normotensive male rabbits. The extract was administered intravenously at doses ranging from 2.5-80 mg kg-1. The extract caused a dose-dependent fall in blood pressure and heart rate. 2.5 mg kg-1 of the extract reduced the Mean Arterial Pressure (MAP) from the initial 102.8±4.2 to 96.6±7.3 mmHg and the Heart Rate (HR) from 398.3±8.3 beats/min to 373.1±9.7 beats/min. 80 mg kg-1 reduced MAP and HR to 38.9±3.1 mmHg and 178.3±83.7 beats/min, respectively. Neither atropine nor promethazine inhibited the hypotensive effect of the extract. The acute hypotensive effect of the extract may be partly due to the negative chronotropic effect or to a direct effect on vascular smooth muscle.