Bacterial arthritis still is a common and serious problem at mayor urban medical centers and is one of the most rapidly destructive forms of acute arthritis. The yearly incidence of bacterial arthritis varies from 2 to 10 per 100,000 in the general population to 30 to 70 per 100,000 in patients with rheumatoid arthritis and in patients with joint prostheses. Irreversible loss of joint function may develop in up to 50% of the patients. Despite better antimicrobial agents and improved hospital care, the fatality rate for this medical problem has not changed substantially during the past 25 years. An understanding of the risk factors and the pathogenesis of nongonoccocal bacterial arthritis and other forms of infectious arthritis, primarily in the context of a differential diagnosis and treatment, are important in order to avoid the delay in making a correct diagnosis and to improve the prognosis.