The first case was of a 27-year-old female, who was diagnosed as having mitral valve stenosis with regurgitation, systemic lupus erythematosus and antiphospholipid syndrome at her previous pregnancy. We performed mitral valve plasty, which included open mitral commissurotomy and Kay's annulo plasty. The second case was of a 53-year-old female, who was diagnosed as old myocardial infarction, mitral regurgitation, systemic lupus erythematosus and antiphospholipid syndrome. She underwent mitral valve plasty and coronary artery bypass grafting. Both cases were treated by administration of methylpredonisolone and heparin perioperatively to avoid thrombosis and aggravation of systemic lupus erythematosus. Both patients showed good postoperative outcome without complications. We consider that it is important to perform the plasty as far as possible, and to administer effective anticoagulation treatment to prevent complications for patients in the setting of systemic lupus erythematosus and antiphospholipid syndrome.