Abstract 1. 1. The pharmacological properties of an antispasmodic drug, tiropramide, were studied in isolated smooth muscle preparations. 2. 2. Tiropramide at concentrations of 10 −6 to 10 −4 M relaxed various smooth muscles contracted spontaneously and by smooth muscle stimulants or electrical stimulation. Tiropramide did not interact with all drug-receptors examined, suggesting a pure musculotropic smooth muscle relaxant activity. 3. 3. Tiropramide was found to inhibit both Ca uptake and Ca release in the guinea pig urinary bladder. 4. 4. Tiropramide is considered to be useful to inhibit the contractile response of the urinary bladder, as this organ is mainly innervated by noncholinergic excitatory neurons.