The growing incidence of diabetes mellitus and the continuing epidemic of cardiovascular disease associated with this ailment have induced numerous investigators to seek evidence of pre-clinical disease besides trying to diagnose advanced stages of disease. Although many of the techniques used in the general population to diagnose obstructive coronary artery disease have proven of value, it appears that the overall diagnostic accuracy of these methodologies may be lower in diabetic patients. Furthermore, in the presence of normal results the short-term event rate is considerably higher in a diabetic patient than in the general population. In this chapter, we discuss the current evidence surrounding some of the most popular techniques to diagnose coronary artery disease as well as some emerging techniques for detection of subclinical atherosclerosis.