Background and aims: In patients with type 1 diabetes mellitus (T1D), cardiovascular disease (CVD) events are more common and occur earlier in life than in non-diabetics. Reduced brachial artery distensibility (BrachD) is an independent risk factor for development of CVD. Our aim was to determine if adults with T1D have lower BrachD compared to adults without diabetes and also to determine how age and gender affect the relationship of BrachD with T1D status. Materials and methods: BrachD was measured using the Dynapulse instrument in 829 participants (352 with T1D, 477 non-diabetics). An ANCOVA model was used to test the association of BrachD with age, sex, and T1D, and the significance of an age*sex*T1D interaction. Results: Mean BrachD was lower in T1D patients vs. controls (6.43 +/- 1.46 vs. 7.16 +/- 1.48 % change per mmHg, p amp;lt; 0.0001). In a model adjusted for age, T1D, and sex, the interaction of age*T1D*sex was significant (p = 0.0045). Younger women both with and without T1D had higher BrachD than men with and without T1D, but older women with and without T1D had lower BrachD compared to older men with and without T1D. Women with T1D had a steeper decline in BrachD with age than nondiabetic women. Conclusions: BrachD is lower in T1D patients than in non-diabetics, indicating increased vascular stiffness. Younger females have higher BrachD than males, but the decline with age in BrachD is steeper for women, particularly among those with T1D. BrachD may be an inexpensive, non-invasive method to ascertain increased CVD risk in this population. (C) 2016 Elsevier Inc. All rights reserved.