We experienced a 42-year-old patient who underwent aortic valve replacement and a 63-year-old patient who underwent coronary artery bypass grafting with mediastinitis caused by methicillin-resistant Staphylococcus aureus (MRSA). They were successfully treated with the intermittent mass-irrigation technique. The irrigation device consistent of a irrigation tube which placed in upper half of mediastinum and three suction tubes which placed in lower half. We dripped the wash composed of 0.03-0.05% of Povidone-Iodine with 1,000 ml of physiological saline, for 3 to 5 times a day by condition. After each wash, we cross clamped the drainage tubes and filled mediastinum with 0.5 grams of vancomycin hydrochloride dissolved in 100 ml of physiological saline, dripped from irrigation tube, for 30 minutes. After 9-day irrigation in the former case and 16-day irrigation in the latter case, the culture of drainage turned negative. We presumed that this new method is effective for mediastinitis after cardiovascular surgery.