The diagnostic value of ultrasound for musculoskeletal pathology is well recognized. Ultrasound offers a low-cost, nonionizing, readily available imaging technique for the evaluation of tendons, muscles, soft-tissue masses, cysts, and other fluid collections. These advantages also make ultrasound a valuable tool for guiding a variety of musculoskeletal interventions. Its real-time capabilities permit continuous monitoring of the needle position relative to the target lesion and to surrounding structures such as vessels. Ultrasound can be regarded as the ÒfluoroscopyÓ for soft tissues. Ultrasound therefore can be used to localize and characterize the lesion, monitor the needle position during the procedure, document the efficacy of the drainage or the technique, and be used for follow-up imaging. Procedures that can be performed under ultrasound guidance include aspiration of fluid for analysis, injection of medication (steroids), decompression of cyst, bursitis or joint, abscess and hematoma drainage, treatment of calcific tendinitis, biopsy, and foreign body retrieval.