The purpose of this study is to determine in subjects with type 1 diabetes mellitus: whether glycemic control can be achieved at least as effectively with an insulin regimen involving pre-meal inhaled insulin plus a single bedtime Ultralente injection as with a conventional subcutaneous insulin regimen involving 2-3 injections per day; and the toleration and safety of inhaled insulin therapy and its effect(s), if any, on measures of pulmonary function. This is an open-label, 3-month, parallel, multicenter study. A total of 60 subjects(a total for all sites) with type 1 diabetes will be evaluated in this study. Subjects who successfully complete the 3-month comparative trial will be eligible to receive inhaled insulin in an open-label protocol which has been extended for two consecutive years. In the comparative trial the control condition is insulin injection therapy, given either BID or TID, depending upon the subject's usual(prestudy) administration regimen. The study condition is tid AC dosing of inhaled human insulin plus a single bedtime Ultralente injection. For subjects randomized to both groups, insulin doses will be adjusted to optimize control based on glucose monitoring results. In the extension study, patients may elect to return to subcutaneous insulin or to continue to start inhaled insulin. As in the 3-month trial, insulin adjustments will be based on glucose monitoring results. Safety parameters include pulmonary function testing performed every three months, as well as yearly EKG and chest x-ray. Clinic visits will occur every 4 weeks so that both the safety and efficacy of trial may be monitored.