Abstract 1. 1. Localization of catecholamines in the bladder of Rana temporaria has revealed a dense innervation of muscle by fine varicose fibres containing adrenaline. 2. 2. Levels of acetylcholinesterase compatible with cholinergic function have been detected in fine nerves innervating muscle, in large bundles and in numbers of ganglion cells. 3. 3. Pharmacological studies have indicated that the frog bladder receives both an excitatory cholinergic and an excitatory adrenergic innervation. 4. 4. This pattern of innervation is markedly different to that in the bladder of the toad, Bufo marinus.