Improved technology and the development of high-resolution transducers have made sonography of the structures of the musculoskeletal system possible. The vast majority of scientific reports on the value of sonography for imaging musculoskeletal abnormalities have been written only in the last decade. Sonography has several inherent advantages: it is relatively inexpensive, allows comparison with the opposite normal side, uses no radiation, and can be performed at bedside or in the operating room if necessary. The advent of MR imaging has revolutionized musculoskeletal imaging and may be used in many instances rather than sonography for evaluating the same abnormalities or anatomic structures. It is important, however, to keep in perspective what the different imaging techniques have to offer, and, if one is just as efficacious as the other, the least invasive and least expensive should be chosen whenever possible. The goal of this article is to review the applications of sonography to the evaluation of musculoskeletal disorders including tendon disease, soft-tissue masses, identification of foreign bodies, osteomyelitis, cellulitis, and certain joint abnormalities.