Worldwide, the prevalence of diabetes mellitus is considerably higher. Endothelial cells in healthy arteries are in a quiescent state, which is kept in place by laminar blood and moving cytoprotective substances and secretes a large number of growth factors and cytokines that control various vascular functions. 1-Evaluation endothelial dysfunction by some biochemical markers 2-Evaluation endothelial dysfunction by Doppler ultrasonography study. A case control study to sample of 88 patients with long termT2DM were collected from the department of medicine at Salah-Aldeen General Hospital, Tikrit-Iraq. Assessment endothelial function was evaluated by Doppler study of common carotid artery, measurement carotid intima- media thickness (CIMT), and some biochemical markers. Endothelial dysfunction markers have highly significant increment in T2DM in comparison to control groups. The common carotid arteries had high abnormal intima-medial thickness of (61.4%)in diabetic patients, atheroma represent 17% of diabetic cases.