A network of ECG telephone transmission has been established which uses simple and inexpensive equipment, and which is aimed particularly at arrhythmia monitoring. Hospitals in areas remote from major medical centers are able to transmit to the Toronto General Hospital for expert advice. 400 patients in their homes may transmit to any of these hospitals for monitoring of pacemaker function or intermittent cardiac arrhythmia. Any patients in the Toronto General Hospital not admitted for a cardiac problem may be monitored via telephone by the expert nurses in the coronary care unit if a cardiac arrhythmia should arise. Equipment for the system has been carefully designed to minimize cost and to make it simple to use, particularly for the old or infirm patients in their homes. Transmissions between hospitals meet American Heart Association specifications for ECG recording. Transmissions of arrhythmias from patients' homes are carried out with a reduced low-frequency response. Expert cardiologists find both transmissions acceptable for their particular purpose. Standards should be set for simple, economic transmission systems as well as for those meeting the most stringent criteria.