Copyright © 2001 by Mosby, Inc. Objective: The Diabetes Control and Complications Trial (DCCT) demonstrated that intensive therapy of type 1 diabetes mellitus reduces the risk of development and progression of microvascular complications. The Epidemiology of Diabetes Interventions and Complications (EDIC) study assessed whether these benefits persisted after the end of DCCT. Results for the adolescent DCCT cohort are reported here. Study design: Of the DCCT adolescent cohort (n = 195), 175 participated in EDIC, 151 had fundus photography, and 156 had albumin excretion rate measured at year 3 or 4. The odds of progression of retinopathy and albuminuria from closeout of the DCCT until EDIC year 4 were assessed. Results: In contrast to the 7.4 years of the DCCT, during which mean hemoglobin A1c levels were significantly lower with intensive therapy than conventional therapy (8.06% vs 9.76%; P < .0001), the subsequent first 4 years of EDIC had mean hemoglobin A1c levels that were similar between the former intensive and the former conventional groups (8.38% vs 8.45%). However, the prevalence of worsening of 3 steps or more in retinopathy and of progression to proliferative or severe nonproliferative retinopathy were reduced by 74% (P < .001) and 78% (P < .007), respectively, in the former intensive therapy group compared with the former conventional group. Conclusions: These findings provide further support for the DCCT recommendation that most adolescents with type 1 diabetes receive intensive therapy aimed at achieving glycemic control as close to normal as possible to reduce the risk of microvascular complications.