Acarbose (Glucobay-Bayer) is the first in a new class of oral antidiabetic drugs, the alpha-glucosidase inhibitors. It is licensed for the treatment of patients with non-insulin-dependent diabetes mellitus (NIDDM), either as first-line therapy when dietary measures are insufficient, or as an adjunct to conventional oral therapy where glycaemic control is suboptimal. The manufacturer claims that acarbose "can achieve a new level of blood glucose control in diabetes". In this article we consider whether acarbose offers any real advance.