Nerve growth factor (NGF) was localized in the mouse submandibular gland by means of indirect immunofluorescence applied to 0.5 micron-thick sections of freeze-dried, plastic-embedded tissue. The antibody to NGF (IgG-fraction) was raised in rabbits immunized with pure 2.5 S NGF from submandibular glands of adult male mice. In the male gland anti-NGF bound selectively to the secretory granules was present in the cells of the granular ducts. Immunoreactive granules extended from the perinuclear region toward the apical pole. In the female gland immunoreactive cells and granules were considerably less abundant than in males. Immunofluorescence was confined to individual secretory cells located in the wall of the granular striated duct. In the present study no support was found for the hypothesis suggesting that immunoreactive NGF is formed within the secretory granules during their transport from the perinuclear region to the apical pole.