Relations between the neurosecretory and adrenergic fibers and the glandular cells of the intermediate lobe of the hypophysis in albino mice were studied by means of light, fluorescence, and electron microscopy. A thin connective tissue layer is situated between the neural and the intermediate lobes. A few connective tissue septa leaving a connective tissue layer penetrate deep into the tissue of the intermediate lobe. The connective tissue layer and septa usually contain capillaries. Basement membranes separate this layer from the tissue elements of both lobes. The neurosecretory fibers enter the intermediate lobe of the hypophysis along the connective tissue septa as well as directly from the tissue of the neural lobe. The neurosecretory fibers entering the tissue of the intermediate lobe form some small enlargements contacting with the glandular cells. In the zones of contact, plasma membranes of the neurosecretory terminals and the glandular cells retain their constant thickness and osmiophilia on their whole length. They are separated from each other only by a 150–200-Å space. A concentration of elements of the granular endoplasmatic reticulum and of polysomes is observed in the cytoplasm of the glandular cells of the intermediate lobe of the hypophysis at the place of such contacts. Using the histochemical fluorescence method for the detection of monoamines, a network of adrenergic fibers showing a yellow-green fluorescence was found around the glandular cells of the intermediate lobe. The intensity of the fluorescence varied markedly from animal to animal. Fibers containing dense core vesicles of 500–900 Å in diameter have been observed in the same region as the adrenergic fibers. The former make synaptic contacts with the cells of the intermediate lobe. Structural peculiarities and functional significance of contacts of neurosecretory and adrenergic fibers and the glandular cells of the intermediate lobe are discussed.