© 2018 by the American Diabetes Association. OBJECTIVE To determine whether the duration of diabetes and duration of prediabetes estimated during a 25-year period in early adulthood are each independently associated with coronary artery calcified plaque (CAC) and abnormalities in left ventricular structure and function later in life. RESEARCH DESIGN AND METHODS Participants were 3,628white and black adults aged 18-30 yearswithout diabetes or prediabetes at baseline (1985-1986) in the Coronary Artery Risk Development in YoungAdults (CARDIA) Study. Durations of diabetes and prediabeteswere estimated based on their identification at examinations 7, 10, 15, 20, and 25 years later. CAC was identified by computed tomography at years 15, 20, and 25. Left ventricular structure and function were measured via echocardiogram at year 25. RESULTS Of the 3,628 individuals, 12.7% and 53.8% developed diabetes and prediabetes, respectively; average (SD) duration was 10.7 (10.7) years and 9.5 (5.4) years. After adjustment for sociodemographic characteristics and other cardiovascular risk factors, and mutual adjustment for each other, the hazard ratio for the presence of CAC was 1.15 (95% CI 1.06, 1.25) and 1.07 (1.01, 1.13) times higher for each 5-year-longer duration of diabetes and prediabetes, respectively. Diabetes and prediabetes duration were associated with worse subclinical systolic function (longitudinal strain [Ptrend<0.001 for both]) and early diastolic relaxation (e9 [Ptrend 0.004 and 0.002, respectively]). Duration of diabetes was also associated with a higher diastolic filling pressure (E-to-e9 ratio [Ptrend 0.001]). CONCLUSIONS Durations of diabetes and prediabetes during adulthood are both independently associated with subclinical atherosclerosis and left ventricular systolic and diastolic dysfunction in middle age.