Background and Objective: The clinical course of type 1 diabetes mellitus (T1DM) has changed in recent decades. The aim of our study was to assess the long-term (> 20 years) clinical status of a patient cohort with T1DM under a specific treatment and follow-up program., Patients and Methods: A single center, observational, cross-sectional study was conducted of a patient cohort diagnosed with T1DM in the 1986-1994 period at our tertiary university hospital. Clinical characteristics, metabolic parameters, and occurrence of chronic complications and comorbidities after > 20 years of follow-up were collected. All subjects entered our specific program for patients with newly-diagnosed T1D and were followed up using the same clinical protocol. Data are shown as mean (standard deviation) or as number of patients and percentage. The appropriate test was used to compare quantitative and qualitative data. A P value <0.05 was considered statistically significant., Results: A total of 279 patients were recorded, of whom 153 (53.6% women; mean age 46.6±8.6 years; age at onset 23.3±8.8 years; disease duration, 23.3±2.6 years) continued to attend our diabetes unit at the time of the analysis. Of these patients, 24.8% were administered continuous subcutaneous insulin infusion (CSII). Mean HbA1c in the past 5 years and in the last year were7.8±0.9% and 7.7±1.1% respectively (7.3±1.5% in those given CSII). Smoking was reported by 19.6% of patients, while 15.7% had high blood pressure and 37.9% dyslipidemia. Diabetic retinopathy was diagnosed in 20.4%, and 11.3% of the total cohort had nephropathy. Only 1.3% of our patients had a history of CVD., Conclusions: Data collected from a cohort of patients with T1DM for more than 2 decades regularly followed up with a specific program in a tertiary university hospital suggest a remarkably low prevalence of diabetic complications., (Copyright © 2016 SEEN. Publicado por Elsevier España, S.L.U. All rights reserved.)