BACKGROUND: Although cardiac devices have been found to reduce symptoms and mortality rates in appropriate patient populations, the implications of certain important risks, such as infection, are incompletely understood. The purpose of this study was to use a large population-based database to define the population that is at risk for cardiac device infections, determine the prevalence of device infections, and study changes in the rates of cardiac device implantation and infection in the past decade. METHODS: Patients with cardiac device implantations and infections were identified with claims files from the Health Care Finance Administration for Medicare beneficiaries from January 1, 1990, through December 31, 1999. Rates of implantation of cardiac devices were determined. Time trend analyses were performed to determine the significance of the observed change in rates. RESULTS: Cardiac device implantation rates increased from 3.26 implantations per 1000 beneficiaries in 1990 to 4.64 implantations per 1000 beneficiaries in 1999, which represents an increase of 42% in 10 years (P for trend <.001). Cardiac device infections showed a larger increase, from 0.94 device infections per 1000 beneficiaries in 1990 to 2.11 device infections per 1000 beneficiaries in 1999, which represents an increase of 124% during the study period (P for trend <.001). CONCLUSIONS: During the previous decade, there was a significant increase in both cardiac device implantations and infections in elderly patients, although the increase in the rates of device infections was substantially higher. Additional studies are needed to better understand the relationship and timing between cardiac device implantation and infection.