Intensive control of blood glucose levels in patients with type 1 diabetes mellitus (T1DM) has long-term effects on kidney function. In the DCCT trial, patients with T1DM were randomly assigned to undergo intensive glycaemic treatment or conventional treatment; 1,375 patients subsequently took part in the EDIC study and were instructed in intensive glycaemic management while receiving treatment at their usual health-care provider. After 18 years of follow-up, the risks of developing microalbuminuria and macroalbuminuria were 45% and 61% reduced, and the risk of glomerular filtration rate <50 ml/min/1.73 m2 was 44% reduced, in patients who underwent intensive treatment during the DCCT.