The sympathetic innervation of the urinary bladder was studied by fluorescence microscopy using glyoxylic methods, and by electron microscopy, in the normal state, after extirpation of hypogastric ganglia and administration of 6-hydroxydopamine. In the normal state adrenergic fibres could be found along the blood and lymph vessels, within the muscle layers and synaptizing on the surface of the local nerve cells or with other, probably local nerve processes. After extirpation of the hypogastric ganglia, degenerated axons could be observed in the local ganglia and in the connective tissue of the vessels. Many fluorescent fibres could be observed in the muscle layers, too. Four to six weeks after the operation, the animals were treated with 6-hydroxydopamine and no fluorescence was observed. In the muscle layer several degenerated fibres could be found, occasionally in close relation to the smooth muscle cells. It was therefore supposed that part of the sympathetic nerves originates from the hypogastric ganglia and is responsible for the modulation of the local ganglia and the blood supply of the urinary bladder. The other part emanates from the "short adrenergic neurons" and may effect directly the smooth muscle cells.