OBJECTIVES: The objective of this study is to assess and compare the characteristics of relapsing remitting multiple sclerosis (RRMS) patients taking Interferon beta 1b (Extavia) or Interferon beta 1a (Rebif) subcutaneously.   METHODS: A large US administrative retrospective claims database was used to identify patients diagnosed with RRMS and were prescribed Interferon beta 1b (IB1a) or 1a (IB1b) between January 2010 and December 2012 were included in the study. All patients were ≥ 18 years of age and continuously enrolled in the same health plan at least a year. Descriptive statistics and chi-square tests were performed on the data. RESULTS: There were a total of 317 patients on IB1a and 10,190 on IB1b during the study period. Of these, more than 70% of the patients in both groups were females (76.7% vs 74.9%, p=0.484). IB1a patients were older than IB1b (48.57±11.47 vs 46.51±10.63 years, p=0.001) and majority of the patients were in the 40 to 65 years age group (72.2% vs 69.1%, p<0.001). The majority of the patients in IB1a were from Midwest (60.35% vs 35.6%) and the least number of patients were from East (5.4% vs 27.0%, p<0.001). More than half of the IB1b patients were on group coverage (21.5% vs 58.0%) and the majority of the IB1a patients were on unknown coverage (77.6% vs 38.9%, p<0.001). The majority of the IB1b patients prescriptions were on health plan formulary (34.1% vs 65.1%, p<0.001) and were diagnosed with mental health problems (18.9% vs 56.9%, p<0.001). IB1a patients enrolled in the same health plan longer (5.71±3.48 vs 4.52±2.45 years, p<0.001) and submitted more claims (491.72±485.80 vs 377.36±363.13, p<0.001). IB1b patients received more number of days of supply than IB1a (30.47±6.80 vs 31.48±13.55 days, p<0.001). CONCLUSIONS: IB1b patients were younger, on health plan formulary and received more number of days of supply.