OBJECTIVES: To examine annual prevalence and treatment rates of multiple sclerosis (MS) patients using a large US commercial administrative claims database. METHODS: Random sample of 5 million lives from the IMS LifeLink Plus database was used for this analysis. Individuals with ≥1 month eligibility were included in the denominator; those with ≥1 month eligibility and an MS diagnosis (ICD-9-CM: 340.xx) were included in the numerator. Presence of a disease-modifying drug (DMD) was defined as ≥1 claim during the calendar year of interest. Baseline demographics and clinical characteristics were evaluated for each group. Annual prevalence (per 10,000) and treatment rates were reported for each calendar year (2006–2012) and were further stratified by age and gender. RESULTS: MS patients were older than patients without MS (mean age range 46.8–47.7 vs. 34.4-35.1, respectively) and more likely to be female (73% vs. 51%, respectively). Comorbidities such as gastrointestinal disorders (42.8%), hypertension (43.5%), arthritis (24.8%) and anxiety (22.8%) were common among MS patients (2006 estimates). MS prevalence ranged from 16.4/10,000 (2006) to 17.8/10,000 (2010). Similar patterns over the years were observed when data were stratified by sex and age, with absolute rates being higher among women vs. men (24.4/10,000 vs. 8.2/10,000, respectively; 2012; P<0.001) and patients aged 45–64 years (29.4/10,000 vs. 0.4/, 15.6/ and 18.2/10,000 patients aged <18, 18–44 and ≥65, respectively; P<0.001). The proportion of MS patients receiving a DMD increased from 2006 (42.5%) to 2012 (51.2%) (P<0.001). Similar rates and trends in the proportion of patients with a DMD were observed when stratified by gender (42.8% (2006) and 51.3% (2012) [female]; 41.5% (2006) and 50.7% (2012) [male]; both P<0.001).  CONCLUSIONS: In a recent 5-year period, MS prevalence in a large US insured population increased slightly, with a greater increase in the likelihood of DMD use.