It is well known that humans with diabetes have more atherosclerosis and its complications. The causes of this relationship are, however, unclear. Although recent data show that improved glycemic control reduces arterial disease in type 1 diabetes, other studies have shown that subjects with "prediabetes" have more cardiovascular disease before the development of hyperglycemia. Thus, either hyperglycemia and/or lack of insulin actions are toxic to arteries, or metabolic derangements exclusive of hyperglycemia are atherogenic. For >50 years animal models of diabetes and atherosclerosis have been used to uncover potential mechanisms underlying diabetes associated cardiovascular disease. Surprisingly, diabetes alone increases vascular disease in only a few select animal models. Increased atherosclerosis has been found in several animals and lines of genetically modified mice; however, diabetes often also leads to greater hyperlipidemia. This makes it difficult to separate the toxic effects of insulin lack and/or hyperglycemia from those caused by the lipids. These studies are reviewed, as well as more recent investigations using new methods to create diabetic-atherosclerotic models.