To examine the prevalence of and risk factors for low bone mineral density (BMD) (osteoporosis or osteopenia) in Japanese female patients with systemic lupus erythematosus (SLE). We performed BMD measurements by dual X-ray absorptiometry at the lumbar spine and the hip and collected basic and lifestyle-related, clinical and treatment characteristics among 58 SLE patients. Odds ratios (ORs) and their 95% confidence intervals (CIs) were assessed for associations between low BMD and selected factors among SLE patients. The mean BMD ± SD was 0.90 ± 0.17 g/cm(2) at the lumbar spine and 0.76 ± 0.17 g/cm(2) at the hip. The prevalence of osteopenia (2.5 SD < T score < 1 SD) was 50.0% and that of osteoporosis (T score < 2.5 SD) was 13.8% in our SLE patients. After adjustment for age and disease duration, we found the number of deliveries (OR = 5.58, 95% CI = 1.31-26.06; P = 0.02) to be a risk factor for overall low BMD (T score < 1 SD) and a maximal dosage of >50 mg/day of oral corticosteroids (OR = 0.25, 95% CI = 0.07-0.91; P = 0.035) as a preventive factor for low BMD at the lumbar spine. Reduced BMD, especially in spinal trabecular bone, was pronounced in Japanese female patients with SLE, particular in those with a history of delivery. A history of high-dose oral corticosteroids was associated with the preservation of BMD at the lumbar spine, however, further study is needed considering the limited sample size.