The innervation of the human spleen was investigated by the fluorescence method for adrenergic nerve fibers (52 cases) and the enzyme histochemical method for cholinergic nerve fibers (27 cases). The spleens examined were removed by laparotomy chiefly for gastric cancer. Adrenergic nerve fibers were demonstrated at the medioadventitial junction and the media in the trabecular arteries, whereas they occurred at the medioadventitial junction in the central and penicillar arteries. They were not found in the trabecular and pulp veins and venules, sheathed capillaries, avascular trabeculae, white and red pulp, and capsule. Nerves containing only a few adrenergic fibers and nerves without adrenergic fibers occurred close to the trabecular arteries. It was also demonstrated that nerves close to the trabecular arteries contain cholinergic fibers. The present study first verifies histochemically that the human spleen is innervated doubly by adrenergic and cholinergic nerve fibers.