This database has been compiled for the PhysioNet/Computers in Cardiology Challenge 2008. It contains 100 2-, 3-, and 12-lead two minutes ECG records sampled at 500 Hz with 16-bit resolution over a ± 32 mV range, including subjects with risk factors for sudden cardiac death as well as healthy controls and synthetic cases with calibrated amounts of T-wave alternans. The subjects include patients with myocardial infarctions, transient ischemia, ventricular tachyarrhythmias, and other risk factors for sudden cardiac death, as well as healthy controls and synthetic cases with calibrated amounts of T-wave alternans. Since these records come from a variety of sources, some of them have been resampled and scaled from original recordings sampled at higher or lower resolution in order to present them in a uniform format here.