There have been a substantial number of studies indicating that GABA is involved in the modulation of the saliva secretion, but the origin of GABA remains to be elucidated. There have also been studies suggesting that it is highly possible to regard the occurrence of VIAAT as a good marker of GABAergic transmission in extra-brain tissue cells containing GAD. The present study was attempted to examine the localization of VIAAT-immunoreactivity, sites of GABA synthesis, in the submandibular salivary gland. The immunoreactivity for VIAAT was localized in epithelial cells of proximal and distal excretory ducts with the latter more intensely immunopositive throughout the postnatal development until postnatal 8 week (P8W). No immunoreactivity was seen in the acinar cells except for at the newborn stage. In addition, the immunoreactivity for VIAAT was detected in the submandibular ganglionic neurons. It was also discerned in outermost cells of smooth muscle cells of arterioles. In view of the previous report by others that GABA receptor- immunoreactivity is localized in the excretory ductal cells and associated ganglionic neurons of the salivary glands, it is possible that GABA plays roles via paracrine and autocrine secretion in the salivary gland.