The glandular kininogenase kallikrein is known to occur in many mammalian organs and glands but direct histochemical localization has been achieved in only a few cases. Porcine kallikrein was localized in the acinar cells of the pancreas and in the striated and collecting duct cells of the submandibular gland. Incubation of frozen and fixed sections with 1 of the crossreacting antibodies, anti-pancreatic, anti-submandibular or anti-urinary kallikrein Ig[immunoglobulin]G resulted in the same immunofluorescence pattern. There was evidence of a specific fluorescence neither in the acinar cells, nor in the interstitial tissue or blood cells of the submandibular gland nor in the islets of Langerhans, the interlobular ducts or blood vessels of the pancreas. From all data now available about glandular kallikreins, it seems that the kallikreins in these organs are very similar.