A 12-lead electrocardiogram (ECG) recorded in patients with acute coronary syndrome (ACS) was transmitted to a call centre via telephone (tele-ECG). In 120 patients (mean age 64 years) referred to hospitals because of ACS, a standard 12-lead ECG and a tele-ECG recorded at the same time were compared by two cardiologists and one internist independently and blindly. Conduction times exhibited very good agreement between standard and tele-ECG with reliability coefficients (R) of 0.91, 0.86 and 0.89 for the PQ-, QRS- and QT interval, respectively. Rhythm analysis was correct in 99% of the cases. Negative T waves, ST-segment elevation and depression were detected with very high agreement in the tele-ECG exhibiting kappa (k) coefficients between 0.75 and 0.96. The correct ECG diagnosis of ST-elevation myocardial infarction (STEMI) was possible with excellent agreement between standard and tele-ECG, showing k coefficients of 0.96, 0.99 and 0.99, respectively, for three investigators. The 12-lead tele-ECG recorder proved accurate for the detection of acute STEMI.