We examined the use of 23 diagnostic procedures and monitoring tests for users of disease-modifying therapy (DMT) and non-DMT users with multiple sclerosis (MS). The Medstat MarketScan(®) Commercial Claims and Encounters database (2003-2007), which is composed of medical and pharmacy claims for approximately 8 million beneficiaries from 45 US commercial health plans, was used to identify DMT users with an index claim for an MS drug and a 6-month baseline period without MS drugs. Patients were followed for 12 months. Logistic regression models were used to estimate differences in rates and proportion of patients receiving procedures and tests between cohorts. Baseline rates for DMT users (n = 12,455) included MRIs (76.8%), spinal taps (15.7%), neuropsychological testing (4.7%), chemistry panels (61.4%), complete blood cell counts (76.7%) and liver function tests (60.5%). Relative to non-DMT users (n = 25,534), DMT users were more likely to receive an MRI, neuropsychological testing, chemistry panels, complete blood cell counts and liver function tests.