A 64-year-old woman who admitted because of abdominal pain and ascites. She was diagnosed as having systemic lupus erythematosus (SLE) and lupus peritonitis based on anti ds-DNA antibody, ANA positive, serositis and renal dysfunction. She was successfully treated by intravenous pulse therapy with methylprednisolone, but her enteritis recurred after switching to oral administration. She recovered following pulse therapy with methylprednisolone and extracorporeal apheresis. This case was characterized by a rather old age of onset and the peculiar initial symptoms of peritonitis.