Silent myocardial ischemia (SMI) has been demonstrated in 2 to 5% of subjects in totally asymptomatic population, in 30% of patients with history of previous myocardial infarction and in 60 to 100% of patients with stable or unstable angina pectoris. In these patients, 60 to 80% of transient episodes of ischemia are silent and SMI is induced by daily activities and so can be registered during continuous ECG monitoring. The finding of SMI during an exercise testing or during ambulatory monitoring has an unfavourable prognostic significance both in apparently asymptomatic subjects and in patients suffering from stable or unstable angina pectoris or survivors to a myocardial infarction. Stress testing and Holter monitoring are the most used non invasive tests to detect SMI. The sensitivity and specificity of ergometer test can be improved by 201-Tl myocardial scintigraphy. Moreover, the ergometer test can be used as a provocative test to induce changes in regional wall kinesis and so these alterations can be evaluated by using echocardiogram and radioisotopic or contrast ventriculography. The echocardiogram allows to evaluate the presence of kinesis changes induced by stress test or by pharmacological stimulation with dipyridamole or dobutamine. SMI can be also detected through the study of metabolic alterations during cardiac catheterism.