The efficacy of a tele-ECG transmission system for transmission of electrocardiograms from ambulance to Osaka City University Hospital for 59 patients with out-of-hospital cardiac arrest was evaluated from December 1992 to November 1993. Authorized emergency life saving technicians (ELSTs) transmitted electrocardiograms by automobilephone connected with electrocardiogram from the location of out-of-hospital cardiac arrest recognized by them to the ICU. Successful tele-ECG transfer was achieved in 34 cases (57.6%). The most common reason for failure of transmission was interference by large buildings located in our urban location, which occurred in 12 of the 25 cases. Defibrillary shock was applied in 9 of 10 cases of ventricular fibrillation, and one patient among them could return to work. In most cases, laryngeal mask airway insertion was performed. The group with tele-ECG transmission required longer time for transfer to the hospital. The time required for insertion of the laryngeal mask airway and tele-ECG transmission appeared to be the main reason for the delay in transport. Although use of tele-ECG transmission can be useful for patients with out-of-hospital cardiac arrest, further improvement on the transmission system will be needed.