Abstract: The tincture of the flowers of Thevetia peruviana was studied pharmacologically. It had a prompt cardiotonic effect on cats and frogs. Under the influence of this herb the tonicity of the heart muscle was increased, the amplitude of the heart beat was increased and the heart rate became slower. The cat unit of the flower of Thevetia peruviana was found to be approximately 0.119±0.0059 g/kg. The drug was almost entirely excreted from the animal body within 24 hours. Accumulation was low. It exhibited a stimulating effect on smooth muscles of the uteri and small intestines in cats, rabbits and guinea-pigs but not in rats.