Infection of bone, osteomyeLitis, is an important pubLic health problem worldwide. It can be primary by hematogenous spread, or secondary to injury or surgery. Bacteria, especially Staphylococcus aureus, are the usual causative organisms, but fungi may also be causative. The pathophysiology involves specific mechanisms by which the pathogens evade host defense (notably biofilms) and host responses leading to local and systemic inflammatory responses. A variety of host factors may increase the LikeLihood of osteomyeLitis and influence the course of disease. Diagnosis is based on cLinical presentation, laboratory and radiographic findings, and microbiologic cultures. Treatment includes surgical debridement and antibiotic administration, and complex reconstruction of resulting bone and soft tissue defects may be necessary. CompLications such as septicemia, septic arthritis, chronic infection, and pathologic fracture are frequent. Animal models are available for primary and secondary osteomyeLitis and provide insight into host and pathogen interactions.