The metabolic and microcirculatory abnormalities associated with insulin-dependent diabetes mellitus involve most organ systems, including the lung. The adverse effects of diabetes mellitus on the function of the respiratory system are minor compared to the morbidity sustained by the cardiovascular, renal, neural, and ophthalmic systems. Nevertheless, physicians should be aware that some indices of pulmonary function may be abnormal in diabetic patients, independent of the more commonly recognized respiratory risk factors.