A patient with invasive breast cancer is treated inside a clinical MR scanner using MRI-guided focused ultrasound through the intact skin. The tumor is outlined on MR images, treatment planning is performed, and short ultrasound pulses are delivered in a computer-controlled fashion until the entire target is covered (top panel). The temperature elevation during each ultrasound pulse is monitored noninvasively using MRI-based thermometry. The bottom panel shows the temperature distribution with the hot spot of a single ultrasound pulse inside the breast. The consequence of the ultrasound thermotherapy is interruption of tumor blood flow and homogeneous tumor damage with loss of proliferative activity as demonstrated by open surgery five days after ultrasound therapy. This combination of image guidance and computer-controlled minimal invasive therapy may represent an ideal vision of tumor surgery, with the human body remaining completely intact. For details, see the article by Huber et al. on p. 8441 of this issue.