The chance observation by Janbon in 1942 that p‐aminosulfonamide caused hypoglycemia initiated an extensive search for oral hypoglycemic agents for diabetes mellitus. In the 20 years since Janbon's discovery, many agents have been studied. Some of them have been discarded after preliminary animal studies, whereas others have undergone clinical investigation in man before being abandoned. Ten oral hypoglycemic agents have been investigated in our clinic during the past 5 years; however, at the present time, only three of these drugs are currently on the market in this country. Two of these agents are sulfonylureas, and one is a diguanide.