From the US Medicaid Analytic eXtract (MAX) data, containing all billing claims from 2000 to 2004, we identified adults, aged 18 to 65, with incident SLE (≥3 SLE ICD-9 codes (710.0), >30 days apart, with 24 months of prior enrollment without SLE claims). Sex, age, race/ethnicity, ZIP code, and geographic region were obtained. We determined health professional shortage areas, number of state-level rheumatologists, and county-level SES using a validated composite of US Census variables. Our outcome measures were use at any time of corticosteroids, hydroxychloroquine, or an immunosuppressant (azathioprine, mycophenolate mofetil, cyclophosphamide, cyclosporine or tacrolimus). We used multivariable logistic regression to examine relationships between sociodemographic variables and medication prescriptions.