The inhibitory activity of glucose-induced insulin secretion on isolated rat pancreatic islets and the contractile activity of KCl-depolarized rat aorta rings of the derivatives of 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide are quantitatively analyzed using multiple regression analysis. The study has helped to ascertain the role of different substituents in explaining these observed inhibitory activities. From a derived most significant correlation equation, it was concluded that a less hydrophobic 3-substituent and a less bulky 7-substituent in addition to a 3-aminoisopropyl and a 6-chloro substituent are advantageous to enhance the inhibitory action of a compound towards rat pancreatic islets. On the other hand, the more hydrophobic 6- and 7-substituents augment the contractile activity. The analysis, in this way, provided the grounds for rationalizing the substituent selection in designing the improved potency compounds in the series.