Infection remains a serious complication of left ventricular assist device (LVAD) implantation. We performed a cohort study to assess infections among patients who underwent LVAD implantation from October 1996 through May 1999. Thirty-six LVADs were implanted in 35 patients; the mean duration (+/- standard deviation) of LVAD use was 73+/-60 days (total for all patients, 2565 days). Sixteen patients developed surgical site infections (SSIs; rate, 6.2 infections per 1000 LVAD days); 9 were deep-tissue or organ/space infections and 7 were superficial. Other infections included 7 cases of pneumonia (rate, 2.7 cases per 1000 LVAD days), 6 venous infections (rate, 2.3 per 1000 LVAD days), 2 bloodstream infections (rate, cases 0.8 per 1000 LVAD days), 3 urinary tract infections, and 2 skin and soft-tissue infections. Deep SSIs were associated with the requirement for postoperative hemodialysis (P=.02). Overall use of antibiotics was extensive, and a trend toward infection with antibiotic-resistant organisms was noted. Infections were a frequent complication of LVAD implantation. Further studies of interventions for preventing infection in LVAD recipients are warranted.