Optimal glycemic control is essential for the prevention of diabetes-related complications, and the intensive insulin regimens that best resemble physiological insulin secretion are most likely to attain it. However, there are many limitations that preclude the early use of insulin by patients with type 2 diabetes or wider implementation of the intensive regimens in type 1 diabetes. More acceptable alternative routes of insulin administration and effective, noninvasive, patient-friendly delivery systems that alleviate the burden of insulin injections have been researched over the years. To date, only pulmonary inhalation of insulin has become a feasible alternative; it has proved to be as effective and well tolerated as the subcutaneously injected regular insulin and it has a pharmacodynamic profile well suited for mealtime insulin therapy. Several pulmonary insulin delivery systems are in different stages of development, and one (Exubera, Nektar Therapeutics/Pfizer Inc.-Sanofi-Aventis Group) has already become clinically available in the United States and Europe for patients with diabetes. Other noninjectable methods of insulin administration are reviewed.