The electrical properties of a radiotransparent carbon electrode were evaluated and compared with those of a high-quality Ag/AgCl electrode. In order to approach clinical electrocardiographic (ECG) recording conditions, special experimental arrangements for the determination of impedance, phase angle, and noise characteristics were used. It is shown that the carbon electrode provides precordial ECG signals of excellent quality during catheterizations and allows simultaneous use of X-ray examination.<>