OBJECTIVE To evaluate trabecular bone mineral density (BMD) in young ambulatory female patients with systemic lupus erythematosus (SLE). METHODS Bone mineral density (gm/cm2) at the lumbar vertebrae (L1-L4) and at the left femur (neck, trochanter, intertrochanter, and Ward's triangle) was measured by dual x-ray absorptiometry in 46 SLE patients (mean age 31 years, mean disease duration 76 months) and in 108 healthy female controls (mean age 32 years). Twenty-two of the SLE patients were receiving corticosteroids (CS) at the time of the study. RESULTS Lumbar BMD in the SLE patients was less severely reduced than was BMD at the femoral sites, but the SLE group was closer to the lumbar fracture threshold of 0.812 gm/cm2 than was the control group (P = 0.0009). There were no significant differences between the SLE patients currently being treated with corticosteroids and those who were not (P > 0.3). BMD at Ward's triangle and at the femoral neck was not significantly reduced in the SLE patients. Total femoral BMD had a sensitivity of 76% and specificity of 62% in differentiating the SLE group from the controls. The positive predictive value was 61% and the negative predictive value was 89%. The prevalence of osteopenia in the SLE patients was 25%. CONCLUSIONS SLE causes significant trabecular bone loss, which is not due to corticosteroid therapy.