The influence of age, sex, and overt ischaemic heart disease on survival after pacing was studied in a population of 427 patients. The median survival for the whole group was 7.75 years. Women between 55 and 74 years and men between 65 and 74 years enjoyed median survivals in excess of 10 years. Patients over 74 years and men with ischaemic heart disease had median survivals of the order of 5 years and 3 1/2 years, respectively. The findings may help to match generator lifetimes to patient-survival prospects.