A 75-year-old woman required aortic valve replacement for aortic stenosis. She had undergone radical mastectomy and irradiation for left breast cancer 25 years previously, and had chest wall infection secondary to osteoradionecrosis. In spite of preoperative infection controls including surgical debridement, the chest wall was not healed well and colonized with MRSA. However, she was too ill with severe heart failure to wait until the chest wound was negative for MRSA for a valve operation. With the infection remaining, the aortic valve was approached through a right parasternal incision, to exclude the infected sternum from the surgical site, and successfully replaced with a mechanical valve. An internal mammary retractor was useful to avoid fractures of the infected sternum and provided excellent exposure of the aortic root. No mediastinitis or prosthetic valve infection was encountered postoperatively.