Arterial disease is a major diabetic complication, yet the component molecular mechanisms of diabetic arteriopathy remain poorly understood. In order to identify major proteins/pathways implicated in diabetic arteriopathy, we studied the effect of 16-wk untreated streptozotocin-induced diabetes on the rat aortic proteome. Specific protein levels in isolated aortas were compared in six discrete, pair-wise (streptozotocin-diabetic and non-diabetic age-matched controls) experiments in which individual proteins were identified and quantified by iTRAQ combined with LC-MS/MS. A total of 398 unique non-redundant proteins were identified in at least one experiment and 208 were detected in three or more. Between-group comparisons revealed significant changes or trends towards changes in relative abundance of 51 proteins (25 increased, 26 decreased). Differences in levels of selected proteins were supported by Western blotting and/or enzyme assays. The most prominent diabetes-associated changes were in groups of proteins linked to oxidative stress responses and the structure/function of myofibrils and microfilaments. Indexes of mitochondrial content were measurably lower in aortic tissue from diabetic animals. Functional cluster analysis also showed decreased levels of glycolytic enzymes and mitochondrial electron transport system-complex components. These findings newly implicate several proteins/functional pathways in the pathogenesis of arteriosclerosis/diabetic arteriopathy.