Peritoneal vasculitis is a rare and severe clinical manifestation of systemic lupus erythematosus. We report a patient who presented with ascites due to peritoneal vasculitis and cutaneous, articular, hematological and renal inflammatory activity. Treatment with glucocorticoids and immunosuppressive drugs was ineffective. In view of the resistance to different therapies, 4 weekly infusions of 375 mg/m2 of rituximab (RTX) were started, in association with cyclophosphamide pulses during the first and the third weeks. With this treatment strategy, the patient reached a complete response which was achieved in later flares of inflammatory activity (the second and third flares were multisystemic and with ascites again, and the fourth flare with nephritis).