OBJECTIVES: To determine the budget impact of treatment patterns for Multiple Sclerosis (MS) based on national guideline. METHODS: A one-year (October 2006 to September 2007) retrospective database search was conducted to identify medication used, costs, patient adherence and provision. The source of data was the Ministry of Health public available database, called DATASUS. The study were conduct in four steps: 1) Determine the medicines codes in the public list; 2) Establish the relationships among drugs and patients usage, based on national guidelines; 3) Analyze adherence pattern in the most relevant center in Brazil, based on medication consumption; and 4) Determine the budget impact for MS treatment.       RESULTS: Medication for MS was responsible by 13% of high cost medication supplied by Public Sector in Brazil. During the period of analysis the costs and number of patients grew more than 100%, in average 60,000 medications per month were supplied and a total 8.294 patients were treated. Patients treated were distributed among therapeutics alternative as follow: 60.28 % to interferon-1a (two brands), 19.99 % to interferon-1b and 19.74 to glatiramer acetate. Five states out of 27 were responsible by 80% of patients treated. It was possible to detect the beginning of drug association. We found that 26% of patients adhere to disease treatment. Treatment costs was higher than USD 9 millions per month, the distribution of costs is similar to the patients distribution due to fewer combination therapy. CONCLUSIONS: National guidelines permits universal access, but the analysis of treatment patterns points to a high concentration of care and this could be an indicator of health care provision inequalities. Due to the high costs of treatments and the fast patient growth rates new cost-efficient alternatives need to be considered as a way to reduce health system inequalities.