Kininogenase activity in both male and female submandibular gland (SMG) began to increase at 4 weeks of age and reached a peak at 6 weeks of age, and then showed a stable level of activity until 10 weeks of age. The release of kininogenase was stimulated via activation of alpha-adrenoceptors alone in male SMG and via both alpha-adrenoceptors and muscarinic cholinergic receptors in female SMG. This indicates that there is a marked difference between male and female SMG in response to methacholine, e.g., the less granular convoluted tubule (GCT) there is in the SMG, the higher is the percentage release of kininogenase evoked by methacholine. It is suggested from these data that the site of localization of kininogenase in the male and female mouse submandibular gland is different; probably predominantly in the GCT in the male and in the striated duct in the female.