A cardiac electrophysiological study (EPS) is a clinical procedure of supreme utility for the diagnosis of the causes of bradycardia and tachycardia. At present, research is been carried out on a minimally invasive approach of this procedure. Therefore, the authors have developed a modular system between a portable PC and the patient, which is suitable for the development and clinical validation of new noninvasive techniques in cardiac EPS. In this paper the authors describe the interface subsystem which performs the required stimulation energy management as commanded by the output of the special software environment at the computer side. The latter allows easy interactive programming of the stimulation protocols used in standard EPS. Also, it supports atrial (A) and ventricular (V) sequential pacing, and real-time endocardial and surface electrograms processing and screen display. The interface module allows two modes of operation according to the level of energy required in the stimulation protocol: a low energy mode for intracardiac stimulation, and a high energy mode for esothoracic stimulation. Adequate electrical isolation between the PC and patient was incorporated. The functionality and reliability of the system was tested following a rigorous laboratory test procedure.