The purpose of this prospective clinical study is to evaluate the role of combination chemotherapy with rifampin in the treatment of orthopedic device-related infections in which the implant could not be removed. Eleven patients with orthopedic implant-related infections due to staphylococci or streptococci were treated with the implant in situ. Each antimicrobial regimen included rifampin in combination with a 19-lactam antibiotic or ciprofloxacin. The median duration of treatment with rifampin was 86 days (range, 15-336 days) with a median follow-up of >24 months after cessation of therapy. Treatment was successful for 82% of patients. Failures were associated with documented inappropriate treatment. These preliminary clinical data are supported by data from in vitro studies and animal experiments. Combination therapy with rifampin, in particular rifampin and a quinolone, should be considered for patients with orthopedic implant-related infections if the implant cannot be removed.Long-term intravenous therapy combined with a one-or two-stage replacement is frequently necessary for controlling orthopedic device-related infection (ODRI) [1]. New antimicrobial regimens may cure infections that were previously considered as necessitating removal of the device [2]. We previously observed in an animal model that even short-term treatment with rifampin can sterilize implant-related infections due to Staphylococcus epidermidis and Staphylococcus aureus [3][4][5]. The present trial was designed as a pilot study for evaluating whether a rifampin-containing regimen could cure ODRIs rather than only suppress the clinical symptoms. We applied such a regimen to 11 patients who had ODRIs and from whom the device could not be removed.We prospectively observed 11 patients (five women and six men) with ODRIs due to gram-positive cocci who were consulted by physicians from the Division of Infectious Diseases (A