OBJECTIVES: Relapsing-remitting multiple sclerosis (RRMS) is the most common form of multiple sclerosis. Beta interferons have been shown to reduce relapse rates by a third. The aim of this study is assessing the value of subcutaneous interferon beta-1a when compared to other available disease modifying drugs for RRMS patients in Spain.  METHODS: Pharmacoeconomic model based on subcutaneous interferon beta-1a clinical trials efficacy data (relapses and progression of disability both on the medium and long run) and local expert panel. This analysis was undergone from the Spanish National Health System (SNHS) perspective, included only direct medical costs and employed an annual discount rate of 3% on both costs and health outcomes. The model provided estimations of cost per avoided relapse and cost per avoided progression, as well as probabilistic sensitivity analysis with 1000 Monte Carlo simulations. Budget impact analysis was also undergone to forecast the implications of subcutaneous interferon beta-1a increased market share in a 4-year horizon.  RESULTS: Subcutaneous interferon beta-1a and natalizumab result in the lowest MS relapse rates with an estimated cost per avoided relapse of €28,847, €29,918, €36,299, €42,027 and €55,379 when subcutaneous interferon beta-1a, interferon beta-1b, glatiramer acetate, natalizumab and intramuscular interferon-1a are employed. Cost per avoided progression is €150,000-350,000 for each therapy but glatiramer acetate (€651,796). Probabilistic sensitivity analysis confirmed subcutaneous interferon beta-1a and interferon beta-1b as the most cost-effective therapies (confidence intervals remained below €45,000 per avoided relapse). Estimated budget impact of assuming 5-9% annual increase of subcutaneous interferon beta-1a market share equals 0.17-0.52% of actual RRMS cost in Spain. CONCLUSIONS: Subcutaneous interferon beta-1a is an efficient strategy for RRMS in Spain as it allows an appropriate management and treatment of RRMS relapses and progression with a minor budgetary impact for SNHS.