High intensity focused ultrasound (HIFU) is a technique that was first investigated in the 1940s as a potential method of destroying selective regions within the brain to aid neurobehavioral studies. A beam of ultrasound can be brought to a tight focus at a distance from its source, and if sufficient energy is concentrated within the focus, the cells lying within this focal volume are killed, whereas those lying elsewhere are spared. This is, therefore, a noninvasive method of producing selective and "trackless" tissue destruction in deep-seated targets in the body without damage to overlying tissues. This technique is being investigated in a number of medical fields, including urology, ophthalmology, and oncology. The mechanism for cell killing is mainly thermal in origin. Renewal of interest in this technique is due to the availability of sophisticated medical imaging, which now allows the focal volume to be accurately targeted and also allows the tissue destruction to be monitored during treatment. The burgeoning field of HIFU focused ultrasound surgery (FUS) are reviewed in this article.