The interpretation of electronic pacemaker rhythm strips requires attention to detail to determine the appropriate function of a pacemaker. Often the clinician is faced with the admission of a patient who is either unknown to have a pacemaker, or the type of pacemaker is not immediately available to the practitioner. In such a situation, the practitioner must be able to use pre-existing skills to determine the proper function of the pacemaker as well as any abnormalities in its pattern. This evaluation requires review of the inherent or underlying patient rhythm, the presenting pacemaker rhythm, and the relationship of the two. Additionally, in more sophisticated pacemakers, the relationship between the functions of the pacemaker also must be assessed. A variety of pacemaker rhythm examples are used to delineate the process involved in the determination of proper pacemaker function.