The objective of this study is to estimate the total numbers of patients receiving implantable cardiac pacemakers initially or as replacement devices in non-federal U.S. hospitals, and to determine the age, sex, and cardiovascular health status of recipients. Projected numbers and characteristics of hospitalized patients receiving pacemaker implantation were determined using a massive, nationally representative inpatient discharge database. An estimated 151,166 patients (53% male, 47% female) had cardiac pacemakers implanted in U.S. community hospitals in 1992. Of these, 21,747 (14%) had previously implanted devices replaced. The age distribution of pacemaker recipients was as follows: under 20 (1%), 20-39 (1%), 40-59 (6%), 60-69 (16%), 70-79 (38%), 80-89 (32%), over 90 (6%). An estimated 115 patients received a replacement device subsequent to an initial implant during the same hospital stay. Atrial fibrillation was diagnosed in 29% and atrio-ventricular block in 42% of patients. Death occurred in 2% of pacemaker recipients before discharge. In conclusion, a significant proportion of pacemaker implants are replacement devices. Substantial differences in age and cardiac health status exist among pacemaker recipients.