Cardiovascular disease (CVD) is the leading cause of death in many developed countries. There is a need for cardiovascular monitoring devices that can supplement traditional medical and clinical care by enabling the diagnosis of conditions with infrequent symptoms, the timely detection of critical signs that are precursors to sudden cardiac death, and the long-term management of chronic conditions through monitoring of symptoms, risk factors, and the effects of therapy. This paper provides an overview of ambulatory electrocardiogram (ECG) monitors, which are one of the most widely prescribed diagnostic procedures for cardiovascular disease. The engineering challenges associated with ambulatory electrocardiography are discussed, and technological improvement areas that are the focus of current research effort are reviewed.