Fifty-eight patients who had at least two episodes of gram-negative bacteremia were evaluated to define the epidemiology of recurrent bacteremia caused by these organisms. Thirty-two patients (55%) had single relapses, 16 (28%) had one reinfection, and 10 (17%) had more than one recurrence of bacteremia. Intravenous catheters were the most common probable source of bacteremia. Relapses occurred earlier after the initial episode than did reinfections (58 days vs. 292 days; P = .002). The duration of antibiotic therapy for the first episode was shorter for patients with relapses than for those with reinfections (13.9 days vs. 17.5 days; P = .046). Microorganisms causing recurrent bacteremic episodes were not unusually resistant to antimicrobial agents. Reinfections may be difficult to prevent because they are associated with the severity of the underlying illness, which may not improve. The frequency of relapses might be reduced by increasing the duration of antibiotic therapy and eliminating foci of infection.