This part of ISO 5841 specifies requirements for reports on the clinical performance in humans of population samples of pulse generators or leads, intended for long-term implantation as cardiac pacemakers, hereinafter referred to as devices. It includes general requirements for all reports and supplementary requirements for reports on cumulative experience with devices and estimates of future clinical performance for devices, when appropriate. Annex A provides requirements for categorizing devices. Annex B provides guidelines for statistics, including a discussion of application of the results obtained. As with other statistical methods, the benefit of the analytical methods in this part of ISO 5841 is limited by the size of population under consideration. Annex C gives the rationale for this part of ISO 5841.