The purpose of this study was to evaluate serum leptin levels in systemic lupus erythematosus (SLE). Forty-one women with SLE were compared with 23 healthy women of similar age and body mass index (BMI). Clinical characteristics and Mexican systemic lupus erythematosus disease activity index (Mex-SLEDAI) score were assessed. Serum leptin levels (ng/dl) were measured by enzyme-linked immunosorbent assay (ELISA). Comparisons of leptin levels were made with the Mann-Whitney U-test. In a multiple regression analysis, those factors that could influence the leptin levels were adjusted. Patients with SLE had higher leptin levels than the control group (SLE median 31 vs control median 15, P=0.023). After adjusting by other variables, the serum leptin levels remained higher in SLE than in controls (P=0.02). Patients with SLE had no association between leptin levels and Mex-SLEDAI score, age, duration of disease, or prednisone doses. Those with SLE had higher leptin levels than controls. Further longitudinal studies are required to evaluate the role of this hormone in the exacerbations of SLE.