3-(Alkylamino)-7-halo-4 H-1, 2, 4-benzothiadiazine 1, 1-dioxides were synthesized, and their activity on rat-insulin-secreting cells and rat aorta rings was compared to that of the KATP channel activators diazoxide and pinacidil. Structure-activity relationships indicated that an improved potency and selectivity for the pancreatic tissue was obtained by introducing a fluorine atom in the 7-position and a short linear (preferably ethyl) or cyclic ( ...