Background and Aims After the Diabetes Control and Complications Trial (DCCT), the Epidemiology of Diabetes Interventions and Complications (EDIC) study continued to demonstrate persistent benefit of prior intensive therapy on neuropathy, retinopathy, and nephropathy in type 1 diabetes mellitus (DM)., The relationship between control of glycemia and gastric emptying (GE) is unclear. Methods We assessed GE with a 13C-spirulina breath test and symptoms in 78 participants with type 1 diabetes at year 20 of EDIC. The relationship between delayed GE and HbA1c, complications of DM, and gastrointestinal symptoms were evaluated. Results GE was normal (37 participants, 50%), delayed (35 participants, 47%), or rapid (2 participants, 3%). The latest mean HbA1c was 7.7%. In univariate analyses, delayed GE was associated with greater DCCT baseline HbA1c and duration of DM prior to DCCT (P ≤ 0.04), greater mean HbA1c over an average of 27 years of follow up (during DCCT-EDIC, P = 0.01), lower R-R variability during deep breathing (P=0.03) and severe nephropathy (P=0.05) and a greater composite upper gastrointestinal symptom score (P<0.05). In multivariate models, retinopathy was the only complication of DM associated with delayed GE. Separately, DCCT baseline HbA1c (OR 1.6, 95% CI 1.1–2.3) and duration of DM (OR 1.2, 95%CI 1.01–1.3) prior to DCCT entry and mean HbA1c during DCCT-EDIC (OR 2.2, 95%CI 1.04–4.5) were independently associated with delayed GE. Conclusions In the DCCT/EDIC study, delayed GE was remarkably common and associated with gastrointestinal symptoms and with measures of early and long-term hyperglycemia. ClinicalTrials.gov numbers NCT00360815 and NCT00360893.