OBJECTIVE: Despite the demonstrated benefits of glycemic control, patient acceptance of basal/bolus insulin therapy for type 1 diabetes has been slow. We investigated whether a basal/bolus insulin regimen involving rapid-acting, dry powder, inhaled insulin could provide glycemic control comparable with a basal/bolus subcutaneous regimen. RESEARCH DESIGN AND METHODS: Patients with type 1 diabetes (ages 12-65 years) received twice-daily subcutaneous NPH insulin and were randomized to premeal inhaled insulin (n = 163) or subcutaneous regular insulin (n = 165) for 6 months. RESULTS: Mean glycosylated hemoglobin (A1C) decreased comparably from baseline in the inhaled and subcutaneous insulin groups (-0.3 and -0.1%, respectively; adjusted difference -0.16% [CI -0.34 to 0.01]), with a similar percentage of subjects achieving A1C <7%. Although 2-h postprandial glucose reductions were comparable between the groups, fasting plasma glucose levels declined more in the inhaled than in the subcutaneous insulin group (adjusted difference -39.5 mg/dl [CI -57.5 to -21.6]). Inhaled insulin was associated with a lower overall hypoglycemia rate but higher severe hypoglycemia rate. The overall hypoglycemia rate (episodes/patient-month) was 9.3 (inhaled) vs. 9.9 (subcutaneous) (risk ratio [RR] 0.94 [CI 0.91-0.97]), and the severe hypoglycemia rate (episodes/100 patient-months) was 6.5 vs. 3.3 (RR 2.00 [CI 1.28-3.12]). Increased insulin antibody serum binding without associated clinical manifestations occurred in the inhaled insulin group. Pulmonary function between the groups was comparable, except for a decline in carbon monoxide-diffusing capacity in the inhaled insulin group without any clinical correlates. CONCLUSIONS: Inhaled insulin may provide an alternative for the management of type 1 diabetes as part of a basal/bolus strategy in patients who are unwilling or unable to use preprandial insulin injections.