AAtherosclerotic diseases are reported to very frequently occur and decrease the quality of life in diabetic patients. Joint committee meetings of the Japan Diabetes Society and Japan Atherosclerosis Society have been held since 1998. We investigated and discussed the goal of treatment for atherosclerotic diseases in diabetes mellitus. We studied clinical reports on the relationship between diabetes mellitus and atherosclerosis. For the prevention and treatment of atherosclerotic diseases, blood glucose control and other risk factors, including hypertension, dyslipidemia, and body mass index (BMI), should be ameliorated the adequately and cigarette smoking should be stopped. We propose a guideline for treatment of atherosclerotic diseases in diabetes mellitus to prevent diabetic patients from suffering macroangiopathy.