The garlic (Allium sativum L., Amaryllidaceae) has been popularly used in the treatment of diabetes and cardiac complications. In the present work, we have studied the possible mechanisms, sulfonylurea receptor (SUR) selectivity of allicin in diabetic hypertensive rats. Diabetic hypertension was induced by intraperitoneal injection of streptozotocin (50 mg/kg) followed by daily administration of dexamethasone (10 µg/kg, s.c.). Different parameters, blood pressure and blood glucose levels were studied in the rats weekly up to eight weeks. Allicin (8 mg/kg, p.o.) shows potent antidiabetic (*p<0.001) as well as antihypertensive effect (**p<0.001, *p<0.01). It may act as a vasodilator by hyperpolarizing the membrane of normal vascular smooth muscle cells. The hyperpolarization in vascular smooth muscle occurs due to K+ channel opener activity. Antihypertensive effect of allicin is inhibited by glibenclamide, nonselective SUR blocker while combination of allicin with nateglinide, selective SUR1 blocker exerted synergistic antihypertensive effect. The results indicates that allicin is effective in the treatment of diabetic hypertension; through a mechanism that might involve selective opening of SUR2.