Breast cancer is the most prevalent type of cancer, excluding lung cancer, for women in the United States. Left untreated, a malignant primary tumor in the breast can metastasize via the underarm lymph nodes, increasing risk of death. Invasive surgery techniques such as mastectomy and lumpectomy are used to treat breast cancer. Although breast-conserving therapies are successful in tumor removal, these surgeries still involve radical resection of the tumor, postoperative radiotherapy, and undesirable cosmetic effects. More recently, less invasive techniques such as cryotherapy and hyperthermia have gained wide appeal. One hyperthermia technique, radiofrequency ablation (RFA), delivers high-frequency alternating currents to heat tissue. This technique minimizes pain, avoids infections and scar formations, and reduces recovery time. However, RFA still requires a needle-like probe to be inserted directly into the breast to deliver heat. In contrast to open surgery and RFA techniques, ultrasound hyperthermia is the only non-invasive technique that does not require any incisions or percutaneous insertions. Ultrasound hyperthermia uses focused ultrasound waves to destroy targeted tissue. During this procedure, an ultrasound transducer delivers mechanical energy to tissues, resulting in temperature increase and thus cell death. Magnetic resonance imaging can be used to guide this non-invasive treatment, eliminating the need to insert a probe. Possible side effects of the procedure include local pain, skin burns, and sometimes injury to surrounding tissue. Our goal is to use COMSOL to model an ultrasound hyperthermia treatment of a breast tumor using a 2D axisymmetric geometry. By modeling the acoustic pressure field in the breast and surrounding water, we will determine the optimum combination of applied frequency and time to reach 42-45 °C for tumor destruction while minimizing damage to surrounding tissues. A frequency of 1 MHz will be used as a starting point, for which tissue properties are best defined.