The available data on pulmonary function in type 1 diabetes are still conflicting. Recently, restrictive alterations of pulmonary function were demonstrated in type 1 diabetic patients with end-stage renal failure (diabetic nephropathy), whereas patients with kidney failure from other causes had normal pulmonary function test results. In this study, the prevalence and nature of pulmonary dysfunction in type 1 diabetes and the relationship of pulmonary function tests to incipient diabetic nephropathy and metabolic long-term control were analyzed. Pulmonary function tests were performed in longstanding type 1 diabetic patients (n = 39) with normal serum creatinine levels ( 1; % predicted: M 81.2, p 1c measurements) was observed: TLC (% predicted: M r = -0.61, p 1 (% predicted: M r = -0.50, p 1c measurements stresses the importance of optimal metabolic long-term control in type 1 diabetes.