Intervention using ultrasonography includes injection, aspiration, needling (barbotage), nerve block, tumor biopsy, and removal of the foreign body. The principles of disinfection during skin preparation, as well as handling of the transducer and needle should be maintained. The needle could be visualized on the ultrasonographic image, and could be tracked during the intervention. Factors affecting visualization of the needle on ultrasonography include the diameter and the incidence angle of the needle. Ultrasonography can be classified as an indirect technique or a real-time technique according to constant use. According to the angle between the transducer and needle, it can be classified as a lateral approach or a coaxial approach.