The role of ambulatory ECG monitoring (AEM) in the evaluation of anti-ischemic therapy is different in relation to the pathogenesis of myocardial ischemia. In spontaneous angina, caused by a primary reduction of coronary blood flow, the AEM represents the most efficient method to evaluate treatment results. In fact ECG monitoring permits the real evaluation of quantitative therapeutic effects, that is the reduction of the number of ischemic episodes or their abolition; besides it gives information about the treatment effects on the ischemic episodes duration, the ST dislocation entity, the incidence of asymptomatic episodes, the presence of ventricular arrhythmias and the possible different effect of treatment on the ischemic episodes characterized by ST elevation or depression. In patients undergoing anti-ischemic therapy AEM allows to study the temporal course of drug effect in order to achieve the best personal dosage schedule. While no doubt exists about Holter usefulness in the short-term control of the treatment, further data are needed to verify the role of AEM in predicting long-term efficacy of therapy. The role of Holter monitoring in the control of treatment efficacy in effort angina is more limited. However this method can be useful in those patients whose stress test shows only a partial protection in spite of anti-ischemic treatment: in these subjects the application of AEM permits to verify the presence of asymptomatic ischemic episodes that can occur either at rest or because of minimal activity.