The use of high energy focused ultrasound (FUS) waves to destroy tumor tissue in breast cancer is explored. High energy FUS destroys cells by raising the temperature of the treated volume high enough to denature cell proteins and bring about cellular death. The absorbed energy results in extremely high tissue gradients between target cells and surrounding tissue, so the effect of the focused energy is concentrated only at the target, leaving the healthy tissue unscathed. This phase one trial has examined the possibility of ablating breast carcinoma using MRI Guided FUS (MRIgFUS) in place of lumpectomy. Ten female patients underwent the procedure at the Chaim Sheba Medical Center between September 2002 and August 2004, using the ExAblate 2000 (InSightec, Haifa Israel Ltd.). Seven to 10 days after the procedure, all patients underwent standard lumpectomy and axillary sampling to complete standard treatment and to allow pathological evaluation of the procedure. Two patients had a complete pathological response. The remaining 8 patients had varying amounts of residual tumor; 2 had microscopic foci of residual carcinoma, 3 had 10% residual tumor, and 3 had 10-30% of residual tumor. Although still in its infancy, the future role of this type of ablation in breast cancer and other tumors is discussed.