The number of total hip and knee replacements that are performed is growing, resulting in an increased number of procedures undertaken to remove replacements that become infected. The treatment of infected replacements is expensive, creating a strong incentive to avoid infection. Preventive measures such as preoperative intravenous antibiotics and double-latex gloves are useful in this respect. When infection occurs in a knee or hip replacement, various procedures are used. Antibiotic suppression is used when the patient is a poor risk for surgery. Debridement of the knee and administration of intravenous antibiotics is appropriate when infection is diagnosed within 2 weeks of onset. Resection arthroplasty is reserved for large knee implants, such as hinges, in patients with limited functional capacity. Arthrodesis of the knee is undertaken in the young patient with single-joint disease, when two-stage reimplantation fails, or when there are multiple problems such as skin loss, massive bone loss, and virulent organisms. When infection cannot be controlled by any other means, amputation is indicated. For infected hip replacements, debridement of the hip with retention of the prosthesis is often successful. Two-stage reimplantation for the treatment of infected total hip prostheses is more successful than one-stage reimplantation. Arthrodesis of the hip after removal of an infected total hip prosthesis can leave the leg 2 to 3 inches short. The diagnosis and treatment of infected knee and hip replacements is reviewed in detail below.