Objective: To evaluate the pharmacodynamic properties, efficacy, safety, and clinical application of insulin glulisine, a rapid-acting insulin analog, in the treatment of diabetes mellitus in ambulatory and hospitalized patients. Data Sources: Searches were performed with the headings glulisine, insulin analog, [LysB3, GluB29] insulin, insulin glulisine, rDNA insulin, rapid-acting insulin, SoloStar, safety, efficacy, pharmacodynamics, and cost analysts within MEDLINE and PubMed, American Diabetes Association (ADA), the Food and Drug Administration (FDA), and Sanofi-aventis Pharmaceuticals (1990–August 2008). Study Selection and Data Extraction: Phase 1, Phase 2, Phase 3, and postmarketing trials examining the efficacy and safety of glulisine in type 1 or type 2 diabetes were reviewed. Studies published as abstracts and the manufacturer's product information supplemented data absent from clinical trials. Data Synthesis: Insulin glulisine is a rapid-acting insulin with relative equivalence in efficacy and safety to other short- and rapid-acting insulins. Glulisine's onset of action of 20 minutes and 4-hour duration of action allow for bolus administration 15–20 minutes prior to or up to 20 minutes after meals. Clinical trials have demonstrated the safety and efficacy in adults with type 1 or type 2 diabetes. Several studies indicated a statistically significant decrease of hemoglobin A1C (A1C) with glulisine compared with regular insulin (0.10 decrease); however, no difference in A1C control was found compared with insulin aspart or lispro, Significant adverse effects appear to be limited to localized and systemic allergic reactions and hypoglycemia. Conclusions: Insulin glulisine is a safe and effective rapid-acting insulin analog for the treatment of adults with diabetes. Clinical benefit over other short- and rapid-acting insulin products is not established. Addition of insulin glulisine to a formulary should be based on institution-specific availability and cost differences between glulisine, lispro, and aspart in the absence of superiority of clinical efficacy or safety and data beyond 26 weeks.