Since the first cardiac pacemaker was implanted twenty years ago, advances rendered have provided patients with increased reliability and therapeutic efficiency as well as subsequent incrementation in their life expectancy. Technological developments have yielded improvement in the main components such as electrode, the energy source and the electronic circuitry. A variety of leads are available to effect pacing requirements at ventricular and, in part, atrial levels. The introduction of lithium energy sources has prolonged the useful life of pacemakers to more than 8 years. Consumption of current has been reduced by decreasing electrode surface area, shortening of pulse duration and employment of hybrid circuits. Microprocessing of the electronic components have enabled reduced size of pulse generators while providing increased reliability and capabilities for additional functions. Amelioration of electrophysiologic disturbances has been specifically approached through increasing use of atrial and bifocal pacemakers, external programmability and overdrive pacing.