Desmodium pulchellum is a medicinal herb which has been reported to possess anthelminthic effects against the liver fluke (O. viverrini) in hamsters. This report shows pharmacological effects of the herb extracts in concious rats. Locomotion associated with muscle relaxation was obserbed. Meanwhile, rats received the extracts had rapid respiration and became red at ears, nose and feet compared to control rats. These results suggest that the herb has major effects on motor, respiratory and cardiovascular system. Both gripping of mice on inclined plane and locomotion of rats were decreased by the herb extracts. The extract from bark of the root exhibited the most potent effect compared to wooden part of the root, leaves and stem. Intravenous injection of these extracts into anaesthetized rats increased respiratory volume (both expired and inspired air), blood pressure and amplitude of QRS-complex. These results indicate that bark of the root exhibits all of these major pharmacological effects and is the most potent part of the herb.