Sulfonylureas have been available for the treatment of non-insulin-dependent diabetes mellitus (NIDDM) since the 1950s. With the introduction of new oral agents, there is a tendency to discount the value of sulfonylurea therapy. Sulfonylureas have the advantage of multiple formulations, low costs, minimal side effects, and demonstrated efficacy in controlling hyperglycemia. The major disadvantage of sulfonylureas is secondary failure, which may occur with all oral agents as part of the progression of NIDDM. Sulfonylureas should continue to play an important role in the treatment of NIDDM.