OBJECTIVES: Identify the demographic and socioeconomic predictors associated with Rheumatoid Arthritis (RA) patients treated with intravenous (IV) versus injectable tumor necrosis factor inhibitors (TNF-i).  METHODS: Patients with at least two RA diagnoses initiating infliximab, etanercept, adalimumab, and IV abatacept were selected from Medicare database (January 2006 to December 2009). The index date was defined as the initial prescription or IV administration date.  Logistic regression was used to determine covariates that increased the probability a patient was treated with an IV form of TNF-i (infliximab or IV abatacept) as opposed to a subcutaneous injection (etanercept or adalimumab). Medications were also analyzed separately using a multinomial logistic regression model.  Demographic, clinical and socioeconomic status (SES) scores were controlled in the models. RESULTS: Subcutaneous injections were used as the reference category in the regression model.  Patients between ages 65 and 69 were less likely to use IV treatment compared to patients over age 80 (Odds Ratio [OR]: 0.59; p<0.0001]). Females were also less likely to be prescribed IV treatment (OR: 0.76; p<0.0001]).  Patients with medium (OR: 1.46; p<0.0001) and high SES scores (OR: 1.51; p<0.0001) were more likely to use IV treatments compared to patients with low socioeconomic status. For multinomial regression, the reference treatment was etanercept.  Female patients had a lower chance of switching to infliximab (OR: 0.73; p<0.0001) and abatacept (OR: 0.76; p<0.0001).  Patients with an Elixhauser index score >2 were more likely to be prescribed abatacept (OR: 1.45; p<0.0001), but less likely to be prescribed infliximab (OR: 0.86; p=0.0023). Lastly, patients were less likely to switch to adalimumab from etanercept if they had high SES scores.  CONCLUSIONS: RA medication prescriptions are dependent on patient demographic and clinical characteristics.  Gender, socioeconomic status, age, and Elixhauser index are all significant variables in determining the treatment of choice.