Transcutaneous Pacing (TCP) is a rapidly applied “non-invasive” technique that can be used successfully in the hospital, emergency department or field setting (1–9). Although the technique has been studied for three decades (7), it is only in the last few years that commercial units have been widely available. Improvements in pad design (particularly the development of non-metallic electrodes) and pulse characteristics (a pulse width of greater than 20 msec.) have allowed the development of units which may provide high capture rates with a level of discomfort which is tolerable in the conscious patient. Transcutaneous pacing may obviate the need for emergency transvenous pacing; further, it is easily adaptable to the field setting although early application appears to be needed for success (1,2).No study has compared the relative effectiveness of different TCP units, and there are no published data on some of the devices. The purpose of this investigation was to compare the functions of five different external pacemaker units on ten volunteers, in order to determine: 1) what percent of subjects could be captured within the limits of tolerability (the capture rate); 2) how much current was required by each unit to capture (the capture threshold); and 3) the degree of discomfort produced by each pacemaker at the capture threshold.