Catecholamines were measured in the separated intermediate and posterior lobes of the rat after stalk section and bilateral superior cervical ganghonectomy. In the intermeiate lobe, after stalk section, dopamine decreases 96%, norepinephrine decreases 80%, and epinephrine is undetectable. In the posterior lobe, dopamine and epinephrine are absent, and norepinephrine decreases by 70% after the operation. In contrast, bilateral superior cervical ganghonectomy produces only a 40% decrease in norepinephrine in the posterior lobe, and no changes in catecholamines in the intermediate lobe. Our results demonstrate that most of the intermediate and posterior pituitary catecholamines are present in nerve fibers of brain origin, and that the posterior lobe has a dual norepinephrine innervation, partly originating in the superior cervical ganglia.