Prophylactic antibiotics are prescribed frequently for patients requiring permanent transvenous cardiac pacemakers, despite a paucity of data indicating effectiveness. A 10 year retrospective analysis was performed of 298 pacemaker insertion procedures involving 204 patients. On the basis of prestudy criteria relating to timing and dosage of antibiotics, the use of prophylactic antibiotics was judged as adequate or inadequate. There were no postoperative infections in the 108 battery pack replacement procedures despite no or inadequate use of antibiotics in 49 procedures. There were nine infections in the 190 battery pack plus pacing wire procedures for an infection rate of 5 percent. There was no significant difference in infection rate between the group given prophylactic antibiotics and the group given no or inadequate prophylactic antibiotics. Of the 190 battery pack plus pacing wire procedures, no infections occurred in the 50 procedures in which surgical drains were not used (p less than 0.003). In the 140 procedures in which drains were used, there was no correlation between wound infection and absent or inadequate coverage with prophylactic antibiotics. Two severe bacteremic Staphylococcus aureus infections occurred in two patients not given prophylactic antibiotics. The other seven infections were clinically indolent. These results suggest the following: (1) There is no need for prophylactic antibiotics in battery pack replacement procedures; (2) prophylactic antibiotics may decrease the severity of infection in battery pack plus pacing wire procedures; (3) surgical drains should be avoided in battery pack plus pacing wire procedures. A prospective controlled study is necessary to confirm these results.