Despite the availability of consecutive generations of potent broad-spectrum antibiotics, bone and joint infections continue to be serious clinical problems with significant immediate mortality and long-term morbidity. The expected clinical presentations of bone and joint infections are changing because of the prolonged survival of immunosuppressed patients, increase in the numbers of an aging population, and use of more complex orthopedic devices and procedures. To recognize articular infection today, we must learn to identify the clinical settings that promote it and the factors that tend to alter its usual modes of presentation. Delineation of these high-risk clinical situations should raise the index of suspicion for joint infection and provoke earlier diagnosis and treatment. A brief report from New Zealand illustrates the costs of infected total hip prostheses. Seventeen cases of infected hip prostheses required 84 hospital days, as compared with 19 days for noninfected patients, with a mean of three additional operative procedures. Based on average daily hospital costs only, the added cost for one infected joint prosthesis was US $18,000 to $21,000. The estimated cost for a hospital stay for an uninfected prosthesis was US $6,000 and for an infected prosthesis US $24,000 to $27,000, excluding surgeon's fees .