Infections of the musculoskeletal system are commonly seen in clinical practice. Ultrasonography can be an important technique, either as the primary imaging technique, or as an adjunct to other imaging techniques when diagnosing and evaluating infection of the musculoskeletal system. Early diagnosis of musculoskeletal infection has important prognostic implications, and as ultrasound is a rapid, portable, and affordable technique, it can be essential to (1) help establish the diagnosis; (2) determine the size and extent of the infection; and (3) provide guidance for aspiration or drainage. Advantages of ultrasound include wide availability, lower cost, and the lack of ionizing radiation. The use of ultrasound in the setting of musculoskeletal infection will be discussed in this article.