Inhaled human insulin (Exubera) (insulin human [rDNA origin]) Inhalation Powder) has recently been approved in the European Union and the US for preprandial use in adult patients with diabetes mellitus. This formulation of insulin has a more rapid onset, but similar duration, of glucose-lowering activity compared with subcutaneously administered regular human insulin. Preprandial inhaled human insulin provided glycaemic control that was comparable to preprandial subcutaneous regular insulin when added to long- or intermediate-acting subcutaneous basal insulin in patients with type 1 diabetes mellitus. Inhaled human insulin is also effective when administered alone, when combined with oral antihyperglycaemic therapy, or when combined with basal subcutaneous insulin in patients with type 2 diabetes mellitus. Comparable rates of hypoglycaemia occurred in patients treated with inhaled human insulin and in those treated with subcutaneous regular human insulin. Patients treated with inhaled human insulin demonstrated a greater decline in pulmonary function (forced expiratory volume in 1 second [FEV(1)], carbon monoxide diffusing capacity [DL(CO)]) than patients treated with comparator antihyperglycaemic agents; the mean difference between the treatment groups that favoured the comparators was noted within the first several weeks of treatment, and did not change over a 2-year treatment period. This agent has also been associated with significant improvements in some quality-of-life and treatment satisfaction scores, especially when compared with subcutaneous mealtime insulin regimens. Inhaled human insulin is an effective and well tolerated formulation suitable for preprandial use in combination with basal subcutaneous insulin in patients with type 1 diabetes. It is also well tolerated and effective in patients with type 2 diabetes when administered alone, when combined with oral antihyperglycaemic therapy, or when combined with basal subcutaneous insulin.