To review the clinical pharmacology of acarbose, an alpha-glucosidase inhibitor, and to summarize its role in the pharmacotherapy of diabetes mellitus. A MEDLINE search identified all relevant articles, including reviews; Bayer Pharmaceuticals. Due to the large number of clinical trials available, specific criteria were used to narrow the focus of this review: (1) randomized, double-blind, placebo-controlled, parallel-group study design; (2) a minimum of 25 patients enrolled per treatment arm; (3) a treatment duration of 90 days or more; and (4) adherence to Food and Drug Administration Good Clinical Practice guidelines. All clinical trials that were available up to December 1995 were reviewed. Preliminary trials and unpublished reports were not reviewed. Acarbose is effective in reducing postprandial hyperglycemia. It does not stimulate endogenous insulin secretion and, therefore, will not cause hypoglycemia when used as monotherapy. The enhanced glycemic control achieved with acarbose is additive to that of sulfonylureas. It lowers postprandial serum glucose and insulin concentrations and does not promote weight gain. Acarbose can be used as first-line therapy with diet and exercise, or it can be used in combination with sulfonylureas to lower hemoglobin A1c concentrations an additional 0.5-0.9%. Acarbose is not a cure for diabetes, nor is it a substitute for diet, exercise, oral hypoglycemic agents, or insulin. Adverse effects are gastrointestinal and can be diminished by starting with an initial dosage of 25 mg tid. Depending on patient response, the dosage can be increased up to a maximum of 100 mg tid over time. Acarbose, through its unique mechanism of action, appears to be a safe and effective adjunctive agent to diet/exercise therapy or sulfonylurea therapy for treatment of non-insulin-dependent diabetes mellitus.