The time of occurrence of cardiac pacemaker problems after implantation was identified to assess the adequacy of published federal guidelines for clinic and transtelephonic follow-up. One hundred eighty-nine pacemaker patients' charts were examined retrospectively to identify pacemaker problems: inadequate sensing, non-capture, battery failure, myoinhibition, muscle stimulation, and inadequate threshold safety margin. Twenty-nine patients (15%) were identified as having pacemaker problems. A total of 41 problems were identified, of which 28 (68%) were corrected by reprogramming. Sixty-one percent of the problems were found during a clinic visit. Problems occurred more frequently during the first year in dual-chamber devices (62%) vs single-chamber devices (35%). During years 1 to 4, when few problems are expected, 30% of all problems of single-chamber devices occurred and 39% of all problems of dual-chamber devices occurred. This is a period of time that Medicare guidelines allow for one clinic visit per year for single- and two visits per year for dual-chamber devices. These data suggest: (1) Many pacemaker problems will be missed with transtelephonic follow-up alone. (2) The majority of problems involving dual-chamber devices occurred in the first year. (3) For both dual- and single-chamber devices, an unexpected significant percentage of problems occurred in 1 to 4 years. (4) Medicare guidelines may be inadequate for follow-up during this time period.