The Cardiotrak is a small, lightweight device originally developed for use by pacemaker patients to transmit their electrocardiograms (ECGs) by telephone to their doctor or to a hospital. The Cardiotrak seemed well suited for use by paramedics and was field tested on 76 patients. In 69 patients, clear ECGs were transmitted with ease; in the remaining seven, only minor, correctable problems were noted. The Cardiotrak appears to have advantages over other devices used to transmit ECGs to base station hospitals from paramedics.