Abstract: Objective: SLE is an autoimmune disease. The mortality rate and causes are different in the various countries. The present study is done to find out the causes of mortality in the SLE patients in Iran. Methods: This study was retrospective according to medical records of patients who were referred to Rheumatology polyclinic, admitted in Rheumatology ward, ICU, Gynecology and Nephrology wards of Shariati hospital during 10 years, from 1991-2001. Results: Of 2021 recorded patient's file, 165 (7,8%) deaths were already recorded. 84.8% were female and 15.2% male. The duration of disease was 36±12 months. The mean duration of follow up from entering the study till time of death was 25.9±16.8 months. The causes of mortality were as follows: infection (12.1%), respiratory (8.5%), CNS (13.9%), kidney (3.6%), malignancy (1.2%), unknown (7.8%), active lupus (3%), infection with other causes (27.9%), respiratory with other causes (11.5%), CNS with other causes (5.5%) and renal with other causes (4.8%). Conclusion: Infection is the most common cause in SLE Iranian patients, which this rate is compatible with some multi-centric studies. But in some previous studies myocardial infarction was reported as the main cause of death.