Sulfonylureas, which have evolved through two generations since their introduction nearly 50 years ago, remain the most frequently prescribed oral agents for treatment of patients with type 2 diabetes mellitus. Glyburide, glipizide, and glimepiride, the newest sulfonylureas, are as effective at lowering plasma glucose concentrations as first-generation agents but are more potent, better tolerated, and associated with a lower risk of adverse effects. Differences in their binding affinity to the beta-cell sulfonylurea receptor have been described, with preservation of cardioprotective responses to ischemia with glimepiride. Clinical studies have shown glimepiride to be safe and effective in reducing fasting and postprandial glucose levels, as well as glycosylated hemoglobin concentrations, with dosages of 1-8 mg/day. In comparative trials, glimepiride was as effective in lowering glucose levels as glyburide and glipizide, but glimepiride was associated with a reduced likelihood of hypoglycemia and a smaller increase in fasting insulin and C-peptide levels than glyburide, and a more rapid lowering of fasting plasma glucose levels than glipizide. Glimepiride also improves first-phase insulin secretion, which plays an important role in reducing postprandial hyperglycemia. Insulin secretagogues, specifically glimepiride, merit consideration as first-line therapy for patients with type 2 diabetes.