A series of 1-[[p-[2-(acylamino)ethyl]phenyl]sulfonyl]-2-iminoimidazolidines has been synthesized. Compounds from this new class of oral hypoglycemic agents lower blood glucose in normal and in streptozotocin-diabetic rats. Potent analogues were obtained by modification of the acyl residue. 1-[[p-[2-(Crotonylamino)ethyl]phenyl]-sulfonyl]-3-cyclohexyl-2-iminoimidazolidine (44) turned out to be the most potent compound in the normal rat (20 times tolbutamide), and 1-[[p-[2-(5-methylisoxazole-3-carboxamido)ethyl]phenyl]sulfonyl]-3-cyclohexyl-2-imino-imidazolidine (30) displayed the highest potency in the diabetic rat (similar to phenformin).