Background: Microangiopathy and macroangiopathy frequently coexist in type 2 diabetes mellitus (T2DM). Both types of the vascular complications share traditional risk factors but it is not clear whether the presence of microangiopathy, such as diabetic retinopathy, constitutes a predictor of atherosclerosis in carotid arteries in patients with the disease. In this study we looked for the association between diabetic retinopathy and intima-media thickness in carotid arteries of patients with T2DM. Methods: In this case-control study we examined 100 consecutive patients with T2DM in Rasoul Akram Hospital in Tehran, Iran during 2009-2010. We assessed intima-media thickness of carotid arteries by ultrasonography. All patients underwent ophthalmo-logic examination. Results: Diabetic retinopathy was found in 50 (50%) patients. Intima-media thickness was higher in patients with diabetic retinopathy than those without it (0.77±0.17 mm vs. 0.71±0.2 mm, respectively, P=0.041). Moreover, intima-media thickness was more prevalent in patients with proliferative diabetic retinopathy than patients with non-proliferative form of the disease (0.87±0.16 mm vs. 0.68±0.1 mm, respectively, P<0.001). Conclusion: Diabetic retinopathy seems to be associated with increased intima-media thickness of carotid arteries in T2DM. It may be a common denominator of pathogene-sis of microvascular complications and atherosclerosis in T2DM. Evaluations of carotid arteries are to be done by non-invasive methods such as color Doppler sonography for screening and preventing prospective cereberovascular accidents in patients with diabetic retinopathy, especially proliferative retinopathy, in routine ophthalmological examination of patients with T2DM.