A patient is described who developed acute proptosis, a rare complication of systemic lupus erythematosus, 16 years after the onset of the disease. Treatment with intravenous methylprednisolone produced rapid improvement, but swelling recurred a few days later. Intravenous corticosteroid was again effective and was continued orally without further episodes of proptosis. This patient is unusual in the long period of mild disease before the development of systemic complications, and in having antibodies to nuclear ribonucleoprotein but persistently normal titres of DNA-binding antibodies in her serum.