High-intensity focused ultrasound (HIFU) is a technique that was first investigated in the 1940s as a method of destroying selective regions within the brain in neuro-surgical An ultrasound beam 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 a noninvasive method of producing selective and trackless tissue destruction in deep seated targets in the body, without damage to overlying tissues. This field, known both as HIFU and focused ultrasound surgery (FUS), is reviewed in this article.