The respiratory function of 51 insulin-dependent diabetic patients (31 with and 20 without LJM) was studied. The variables age, diabetes duration, height, and metabolic control were similar for both groups. Vital capacity (VC), forced expiratory volume (FEV), mean maximum expiratory flow (MMEF), and FEV/VC ratio were determined before and after the administration of a bronchodilator. VC, FEV, and MMEF showed significantly lower values (p<0.02) in patients without LJM as compared to those with LJM. It is suggested that these alterations may be due to abnormalities of collagen fibers and elasticity in the lung and are not related to reversible bronchial obstruction. We believe that LJM is an extrinsic manifestation of a systemic process, aggravating the prognosis of diabetes mellitus.