Despite its relatively low prevalence in Brazil, multiple sclerosis (MS) is responsible for significant health care expenditures for the public health care system. OBJECTIVES: To compare actual MS treatment expenditures and expected expenditures based on an epidemiological projection. METHODS: We retrieved actual treated prevalence and treatment costs from Brazil’s public health system database for the city of Sao Paulo, in 2009. Then, current prevalence of MS for the city of Sao Paulo was estimated based on the best epidemiological evidence available, a prevalence study conducted in 1997, which reported a prevalence of 15/100,000 inhabitants. Data were analyzed comparing actual and potential expenditure related to drug treatments, assuming that 85% of prevalent cases comprised the relapsing form of MS. RESULTS: We retrieved the total number of doses for each one of the available treatment options for MS in the city of São Paulo for the year 2009 (interferon beta-1A, interferon beta-1B and glatiramer acetate). Considering the expected number of doses required to treat one patient for one year with each treatment option, we estimated the number of patients covered within one year of treatment to be 1,319 patients. This corresponds to an estimated treated prevalence of 11.9 cases per 100,000 inhabitants, considering the estimated population for the year 2009 (11,037,593 inhabitants). Actual costs incurred for the city of Sao Paulo in 2009 with the treatment of MS were R$40,993,666/€18,633,484. Assuming a prevalence of 15/100,000 inhabitants, 1,666 cases of MS would be expected in the city, of which 1,416 would be relapsing MS. Their treatment would require R$43,811,800/€19,914,454. CONCLUSIONS: There are marginal differences between treated and expected prevalence of relapsing MS in the city of Sao Paulo. This indicates that local programs for MS diagnosis and treatment are successful. Likewise, current budget impacted analyses based on epidemiologic information seems accurate.