Abstract: A portable combined pacemaker parameter and vital sign monitor acquires data relating to a patient's ECG waveform and an in vivo pacemaker waveform by means of electrodes which contact the patients's skin near the location of the patient's pacemaker. The monitor detects signals from the pacemaker and displays derived waveforms on a self-contained display screen. The monitor also includes a storage device to store data derived from the detected signals for subsequent recall and analysis. The waveform information is displayed on the monitor so as to show the relationship in time between the ECG waveform and the pacemaker waveform. The monitor is particularly useful for the portable measurement of ECG and/or pacemaker waveforms and for the ongoing analysis of the condition of a working pacemaker in vivo.