Because diabetes mellitus (DM) is considered a major risk factor for cardiovascular disease, the clinical evaluation of the patient with diabetes should include a thorough review of the patient’s medical history, current treatment regimen (oral agents, insulin), related comorbidities (hypertension, obesity, metabolic syndrome, coronary artery disease), resting electrocardiogram (ECG), selected laboratory studies (e.g., blood glucose, hemoglobin A1c, serum creatinine, estimated glomerular filtration rate, urine albumin/creatinine ratio), and ankle/brachial systolic pressure index, if available. A conventional or cardiopulmonary exercise stress test may also be conducted as part of this evaluation. In addition to the indications and contraindications and appropriate methodology (protocols) for exercise testing, key diagnostic and prognostic variables include the resting and exercise ECG, especially the provocation of significant ST-segment displacement and/or arrhythmias during or after exercise testing; anginal symptoms; dyspnea; chronotropic incompetence; abnormal heart rate recovery; exertional hyper- or hypotension; estimated or directly measured cardiorespiratory fitness, expressed as mL O2/kg/min or metabolic equivalents (METs; 1 MET = 3.5 mL/kg/min); and combined information (e.g., treadmill scores [Duke treadmill score]). Adjunctive echocardiographic studies may also be used to identify impaired left ventricular diastolic function, a condition that is common in DM, as well as systolic dysfunction. Collectively, these data should prove helpful in prescribing safe and effective exercise programs and delineating appropriate treatment targets to reduce the likelihood end-organ complications and cardiovascular events in this escalating patient population.