Dilute povidone-iodine solution has been widely used as an irrigant for the treatment of mediastinitis. However, its use is not without adverse effects and often cause? poor prowth of pinulation tissues. To avoid the problems seen with the use of povidone-iodine solution, we applied electrolyzed strong acid aqueous solution (ESAAS) to mediastinal irrigation in 4 patients (2 infants and 2 adults) who developed mediastinitis after cardiovascular surgery. According to the "open" method, the mediastinal wound was left open and irrigated with ESAAS 1 to 3 times a day until the infection was eradicated.Mediastinal infection is an uncommon but lifethreatening complication after median sternotomy. The generally accepted method of therapy for this complication consists of antibiotic therapy and surgical treatment including drainage, debridement, and irrigation. Closure of the wound space with musculocutaneous flaps or omentum is also performed as an optional treatment.Povidone-iodine is an excellent bactericidal and fungicidal agent, and its dilute solution (0.5%) has been widely used to irrigate infected tissues (I). The use of povidone-iodine solution is not, however, free from adverse effects. Growth of granulation tissues is often impeded because povidone-iodine can substantially damage underlying healthy tissues. Thyroid dysfunction ( 2 ) , electrolyte derangement, metabolic acidosis (3,4), and restrictive pericarditis ( 5 ) have also been reported as toxic or adverse effects attributed to the use of povidoneiodine solution.Electrolyzed strong acid aqueous solution (ESAAS) is produced by electrolyzing sodium chloride solution. It has unique and strong sterilizing effects, and no significant deleterious effects due to ESAAS have been re-